US1457898A - Telephone system - Google Patents

Description

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DODG E TELEPHONE SYSTEM Filed Jul 19; @919 2 Sheets-Sheet 1 //4 van/0r W/Mam L Badge b y Amy June 5, 11923.

' W. L. DODGE TELEPHONE SYSTEM Filed July 19, 1919 2 Sheets-Sheet 2 X NUFQ v. m .W.

Patented June 5, 1923.

WILLIAM L. DODGE, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed July 19,

To all whom it may concern:

Be it known that I, WILLIAM L. Donen, a citizen of the United States, residing at Maplewood, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to improvements in signaling systems wherein signals are transmitted over a trunk line extending between widely separated oilices.

Heretofore it has been proposed in the patents to B. Gherardi, Nos. 1,251,363 and 1251364, granted December 25, 1917, to employ a signaling path common to a plurality of telephone trunk lines with apparatus at each end of the signaling path for individually associating therewith the trunk lines in order that the signals incident to the establishing of connections over the trunklines may be controlled over the common signaling path. The present inventlon, which 1s 1n the nature of an improvement over the systems disclosed in the patents referred to above, has for one of its objects the provision of a system of this character in which a greater number of telephone trunk lines may .be served by the common signaling path and in which the signals may be rapidly trans-' mitted over the common signaling path, and

in which the possibility of confusionin controlling the sending and receiving of said signals over the common signaling path is reduced to a minimum.

Another object of the invention is to prevent the operation of a recall signalwhen a subscribers line circuit is opened by single momentary reciprocation of the switchhook.

Other objects of this invention will be ap-v parent from the description hereinafter given.

" i In the embodiment of the invention illustrated herein, the objects of the invention are accomplished by employing at each end of the common signaling path an intermittently operating distributor for sending and receiving thereover code signals, each tele- 1919. Serial No. 312,069.

phone trunk line served by the common signaling path having a diiierent set of code combinations individual thereto so that the particular telephone trunk line will be controlled by the code combination indi-' vidual thereto. I

Inasmuch as the intermittently operating distributors transmit Over the common signaling path the code combinations of a plurality of telephone trunk lines, of which any number may be simultaneously in signaling condition, the present invention contemplates the provision of suitable means of delaying the transmission of the code combinations of a plurality of. such lines simultaneously insignaling condition as well as means fordetermining the orderin which the code combinations of the lines are to be transmitted. As herein diS:'lOS8d, the means for accomplishing these functions is individual toeach line and comprises individual sets of relays whose circuits are so organized that when the relays associated with one telephone trunk line are actuated, the relays associated with allother lines are rendered inoperative. These setsof relays also determine the code combinations to be trans-' mitted by the distributors. I p In order that the transmitted code combinations or signals may be translated into suitable signals for the appropriate telephone trunk lines, this invention contemplates the provision of receiving apparatus which is selectively responsive to the transmitted code combinations or signals to set into operation the signal of the particular telephone trunk line, the code combination. of which has been transmitted. The receiving apparatus, as herein disclosed, is a pyramid relay combination of a type. well known inthe signaling art, provision being made to vary the character of the impulse overthe selected path through the contacts of the pyramidselecting relays determined by the transmitted code ombination for controlling the various signals associated with the particular telephone trunk line.

According to; another feature of this invention, there is but a single receiving con ductor for each telephone trunk line, over which the various signals for the particular particular reference to applying ringing trunk line are controlled. .These signals are controlled by impulse of but short duration *and in order that a plurality of signals may be controlled thereover by these short impulses, provision is made for prolonging;

period. ;This feature has more particular reference to the recall signal which may be the signal resulting from the intermittent operation'of a signaling lamp. It also has curre'ntto the connected telephone line for a definite period of time in order that the signaling device may operate for a prede" termined length of time. As disclosed here- I in, the means for carrying into effect this feature of the invention comprises a pair of signal receiving relays normally connect ed with a single receiving conductor for controlling the recall signal, and a plurality of cooperating slow-releasing relays which serve to maintain a ringing relay energized nection with the accompanying drawings,

fora definite period'of time.

the following description considered incon- Figs; 1 and 2 of which, when placed end to end with Fig. 1 at theleft'of Fig.2, constitute a circuit diagram of one embodiment v of this invention. The apparatus shownin Fig. 1 islocated at the oflice X, that shown to the left of the dotted line 2-2 of. Fig. 2

i's'located atthe oflice Y, while the appara- 1 tu's shown to the right of the dotte'dfline like apparatus is employed at both oiiices X and Y, it will be designated by'the same reference characters that at the office X without, and that at the oflice Y withprimes. Referring to the drawings there is shown a cordcircuit located at the office X for making connections with a telephone trunk v one toll cord cir'cuit,' onetoll trunk line, onelinelfextending from the ofiice X tojthe oflic'e Y. The trunk'line L may be con nected with a toll switching trunk "circuit-H extending from the office Y to the ofiice-Z;

at which terminatesa subscribers telephone line G with. which the toll switching trunk circuit H maybe connected. VVhileonly 1 toll switching trunk and one subscribers telephone lineare shownyit is to be underperviso'ry and other signals between operators and betweenop'erators and subscribers of intermittently distributor RD in connection with the establishment of con nections over the various trunk lines, a signaling path P common to a plurality of trunk lines extends from the central ofiice X to central ofiice Y.

The various trunk lines to which the signalingpath P is common are individually associated with the signaling path. by means operating distributors similar to the soscalled start-stop distributors employed in )ri 1tingtelegraphy. In transmitting signals from the ofiiceX over or transmitting start-stop distributor TD is employed. At the office X there is associated. with each toll trunk line a set of three relays such as K M fl N and KQM N etc. When a signal originates 'at-th'e out going end of one of the trunk lines; signal control leads A; B and C individual there to' are rendered effective to cause the-opera-- tion of the relays of the associated set which thereupon perform the triple function of looking out the relays of other lines on which. signals are originated at the same time, of determining the order in which the signals shall be transmitted and of transi lating such signals into code combinations For a more complete understanding of this"invent1onreference should be hadto or code signals which are transferred toa set of Storing'relays 1'to'5 inclusiveforthe thecommon signaling path P the sending vidual to thetrunk lines, control the po larities of signaling current connected with the individual. sending segments of the send.

ing distributor TD.

At the olficeY the codecombinations or code signals are received by means of an iiiter nlttently operating receiving start-stop d stributor RD 1n orderto translate the i'eceived code signals'intov suitable signals and to select the appropriate line. pyramid selecting relays are prov ded and arej'con-,

trolled by locking relays whose energizing circuits are controlled directly'from the individual receiving segments of the receiving Referring more-in detail tothe apparatus provided at thev office Y for receiving code signals transmitted overthe common signaling path P. the receiving distributon RD is controlled by differential polarized relay 40" connected in the common signaling path'P. Then the alternate contract is first closed, therelease magnet RDM of the re ceiving distributor ED is energized and releases the brush arm controlled thereby which is thereupon rotatedthrough one complete cycle. Relay 39 which is normally energized over a circuit from battery througli segment 1]., the brush arm and segment 12 Offthe receiving distributor RD", holds open its contact which is in the locking circuits of locking relays 41 to 45 inclusive whose energizing windings are connected with the respective individual receiving segments 1 to 5 inclusive, of the receiving distributor RD. Relays 41 to 43' inclusive, control relays 46' to 52' inclusive, comprising the pyramid selecting relay combination which cooperates with looking relay 44; to select the signal receiving leads D terminating in contacts of the relays 46 to 49 inclusive. Locking relay 45 controls the polarity of signaling current connected with the selected'signal-receiving lead for determining the signal to be operated.

For transmittingover the common signaling path P signals originating at the oflice Y, a sending distributor, storing relays and sets of three relays similar to the equipment shown and described in connection with the otfice X are provided. Such sendingequip ment is indicated by the small dotted rec.-

tangle designated SE. In order that the code signals transmitted over the common signaling path P from the office Y may be properly received at the office X, receiving equipment similar to the'receiving distributor RD the pyramid selecting relays and locking relays described in connection with the receiving of signals at the ofiice Y is provided at the office X. This receiving equipment is indicated by the dotted rectangle designated RE.

Having in mind this brief description of the apparatus shown in the drawing it is thought that the invention will be thoroughly understood from a description of the operation of the system as shown.

(loan-action, of 00rd circuit F with tmmlc Zine L oflice Y. communicates with the operator at otlice Y over an order wire circuit (not shown). The operator at the oflice X ascertaining from the operator at the office Y that the connection with the telephone line G is to be completed over trunk line L inserts calling plug 20 of the cordcircuit F into ack 21 of trunk L Relay 22 thereupon operates over a circuit from. battery through super visory lamp 28, sleeve contacts of the plug 20 and the jack 21 and winding of relay 22to ground. Relay 22 in opening its right-hand normal contact causes the release of a normally energized relay 24 and in closing its left-hand alternate contact causes the energization or two slow release relays 25 and 26. Relay operates over a circuit from battery through the letthand alternate contact of relay 22. winding of relay 25 and the normal contact of signal receiving relay 27 to ground while relay 26 is energizedover a circuit from battery through the left-hand alternate contact of relay 22, winding of relay 26, normal contact of signal receiving relay 28 and the normal contact of slow-release relay 29 to ground. The energization of re lay 26 disconnects'the energizing winding of the signal receiving relay 27 from the signal receiving lead or circuit D associated with trunk line L The disconnection of right-- hand winding of signal receiving relay 2'? from the signal receiving lead D prevents the false operation of the signal receiving relay 27 upon the transmission of the first signal from the oftice Y over the common signaling path P as willmore fully hereinafter appear.

Assuming that no other trunk lines are in signal initiating condition at the time of the deenergization of the normally energized relay 24-. the closureof contact 30 thereof causes the operation of relay N over a circuit from battery through the right-hand alternate contact of relay 22, contact 30 of relay 24;, signal control lead B right-hand windingof relay N and the contact of relay K to ground. The circuit which has just been traced is: established irrespective of the condition of relays corresponding to K M N of'higher numbered trunks but is not established if any of the relays of the K group of lower numbered trunks are energized. The relay N upon being energized completes a locking circuit for itself which may be traced from battery through the left-hand winding and alternate contact of relay N and the contact of release relay 31 to ground. Relay N in opening its normal cont-act introduces a break in'the energizing and holding cir cuit of relay K and in closing its-righthand alternate contact causes the operation of relays K and M over'a circuit from battery through the windings of these relays in parallehrright-hand alternate contact of relay l 'and normal contacts of other relay N to N inclusive to ground provided none of the latter relays have been previouslyenergized due to the respective lines being in signal initiating condition. Relay K in operating opens the energizing circuits of relaysN to N inclusive to prevent energization thereof while the line L is in signal initiating condition. If relay N were energized during this time, relays K and M would fail to energize due to the energization of relayN vRelays of the K group may be slow in releasing so that upon the deenergization of the relays of a set the normal contact of the N relay thereof will be closed prior to the closure of the contact ot the K relay. In this-manner it is insured that the signals of the various lines which may be in signal originating condition simultaneously will be transmitted in a definite order. namely, beginning with the highest numbered descending-scale. After the signals corresponding to the lowest-numbered line function, the code signal corresponding to the highest numbered line then in signal originating condition is transmitted.

'Relayl which determines the code of the signal to be transmitted over the common signaling path P, upon being energized closes its right-hand alternate contact, and grounds the signal control lead A causing the energization of relay at over a; circui from batterythrough the right-hand alter-,

nate contact of relay 22, winding of relay 24, contact 32 thereof, signalcontrol lead A right-hand alternate contact of relay M and contacts of slow-release relay 33 and release relay 31 to ground. Slgnal control leads A and B? are thereby rendered ineffective until a subsequent deenergization of relay 24'. Relay 2st upon being energized 7 time function.

alternate contact of relay M causes the 0p-.

eration of storing relay l and start relay 36 ove! 'a'circuit from battery through h windings of start relay 36 and storing re y t and the left-liand alternate contactofrelay M to ground.

Theenergization of storing relay 4 disconnects positive battery from'individu'al sende ing segment dot the sending distributor TD and connects negative battery thereto. It

is to be observed that positive battery is now connected with the other individual sending'segments 1, 2, 3 and 5. The closure of the contact of start relay 36 causes the energization of release magnet'TDM over a circuit from battery through ring 8, the

brush arm and segment 11 of the sending distributor TD, contact of start relay 36 and the winding of release magnet TDM to ground. The release magnet TDM in 'attracting its armature releases the brush arm 7 ofthe sending distributor TD which thereupon makesa complete revolution in a clot-lwise direction successively engaging the various segments thereof. Normally the outer half of the brush arm connects negative battery through segment'r, the brush arm, the "common sending ring le with the common signaling pathP'. Upon engagement of thebrush arm with the starting seg-.

line and proceeding in a ment 8 positive battery is connected with the 7 common signaling path P thereupon causing the energization of the differential polarized relay 10 at the office Y. Asthe brush arm moves out ofengagement with the segment I 11, the release magnet TDM is deenergized restoring its armature to normal position so thatv it may stop the brush arm upon the completion of its cycle and hold it against rotation. The engagement of the brush arm with the segment 12 causes the operation of slow release relay 33 over a circuitfro n battery through ring 8 the brush arm, segment 12 and'the winding of slowrelease relay 33 to ground. This relay 33 thereupon removes ground from the signal control lead A As the brush arm successively engages. the individual sending segments 1 to 5 inclusive, signaling currentofthe polarities connected therewith are successively connected with the'common signaling path P which te:.'-'-

vminates at the ofiice X on the common send ing ring 14:. These polarities are suchthat the sending distributor TD transmits a code signal of five impulses, the first; secon-l, third-and fifth of which are positive and the fourth negative. When the. brush arm moves out of engagement with the segment 12, the energizing circuit of the slow releasing relay 33is opened, and upon the engagement of the brush arm with the segment 13, release relay 31 is energized over a circuit from battery through the ring 8, the brush arm, thesegment 13 and the winding of release relay 31 to ground. Relay 83 is made slow in releasing so that its contact remains open until after the opening of the contact of release relay 31, thereby to prevent the premature operation of any relay 24 of a trunk line in signal initiating position. The

'energization of release relay 31 opens the locking circuit of relay N whichthereupon releases, causing the deenergization of relays M and K Storing relay 4 and start relay 36 release upon the opening of the lefthand alternate'contact of relay 1 brush armsmoves out of engagement with segment 13,-release relay 31 is deenergized, and when the brush arm engages segment a", negative signaling current is connected with thecommon signaling path P. The storing relays 1 to 5 and the sending distributor TD are now in normal condition ready for association with any other trunk line which may'initiate a signal at the office X.

Upon the energization of the diiterential polarized relay 40 due to the transmission of the first positive or starting impulse over the common signaling path P when the brush arm of the sending distributor TD engages its starting segment 8, release magnet RDM of the receiving'distributor RD is energized over a circuit from battery through the alternate contact of the differential pol- As the lib) and segment 8 and the winding of the release magnet RDM' to ground. The attraction of the armature of the release magnet RDM upon the energization thereof, releases the brush arm of the receiving distributor RD which is thereupon rotated through a complete cycle at the end of which the brush arm is stopped in its normal position. As the brush arm moves out of engagement with the segments 13' and 8, the release magnet RDM is deenergized permitting the release of its armature preparatory to stopping the brush arm whenit reaches its normal position. When the brush arm moves out of engagement with the segments 11 and 12', relay 39 is deenergized and closes its 1 contact which is common to the locking circuits of the locking relays 41' to 15' inclusive. The armature of the differential polarized relay assumes its normal position when negative signaling current is connected with the other end of the common signaling path P and assumes its alternate position whenever positive current is connected with the opposite end of the common signaling path P. The brush arms of the sending and receiving distributors TD and RD are being rotated at the same time and in synchronism. Therefore when the brush arm of the sending distributor TD engages the sending segment 4t to which negative signaling current is connected,the armature of the differential polarized relay 40' is in its normal position while the brush arm of the receiving distributor RD engages the receiving segment 4. Therefore locking relay 44; is energized over a circuit from battery through the normal contact of differential polarized relay 40, common receiving segment 10, the brush, arm, individual receiving segment 4: and the upper winding of locking relay 44' to ground. Relay 44: immediately locks up over a circuit from battery through the contact of relay 39, the lower alternate contact, of relay 4:4 and the lower winding thereof to ground.

Upon the subsequent engagement of the brush arm of the receiving distributor RD with segments 6 and 7 signal receiving relay operates over a circuit from negative battery through the normal contact of lock ing relay i5, segment 6, the brush arm and segment 7 of the receiving distributor RD, upper alternate contact of locking relay 4%, the lower normal contacts of pyramid selecting relays 5a. 51 and'tt), signal receiving lead D and the left-hand winding of signal receiving relay to ground. Signal receiving relay thereupon completes a locking circuit for itself from battery through its middle alternate contact and right-hand winding to ground; and causes the lighting of supervisory lamp 57 over a circuit from hattery through the lamp 57, lower normal con tact of relay 58 and theleft-hand alternate contact of signal receiving relay 55 to ground. The lighting of this supervisory lamp 57 is an indication to the operator at the office Y that connection has been made with the proper trunk line, in this case trunk line L", by the operator at the office X. The right hand or energizing winding of signal receiving relay is connected through the contact of slow-release relay 110 with the signal receiving lead D and therefore in parallel with the left-hand or energizing winding of signal receiving relay 55, so that signal receiving relay 75 is energized at the same time as signal receiving relay 55. This signal receiving relay 75 does not however lock up, for its locking circuit is open at the contact of the slow-release relay 74. Therefore the energiz ation of signal receiving relay 7 5 at this time performs no useful function. When the brush arm of the receiving distributor RD moves out of engagement with the segments 6 and 7, energizing circuits of signal receiving relays 55 and 75 are opened, causing the deenergization of signal receiving relay 75. vVhen the brush arm engages the segments 8 and 18 the armature of differentialpolarized relay 4:0 is in its normal position, for the brush arm of the sending distributor TD is now in engagement with segment 1" and negative sig naling current is connected with the common signaling path P. The energizing cir cuit of the release magnet RDM is therefore open at this time. The engagement of the brush arm with the segments 11 and 12 causes the energization of relay 39 which thereupon opens the locking circuit of relay 44c. The recelvmg equipment at the office Y 18 now in normal condition ready for receiving any further transmitted code signals resulting from signals initiated by any other trunk lines at the ofi'ice X.

Connection of toll switching trunk circuit H with telephone Zine 6'.

At the time the operator at the office Y designated the trunk line with which the operator at the office Y. should connect the cord circuit 1*, the operatorat the oilice Y also communicated with the oifice Z over an order wire circuit (not shown) advising the operator thereat the number of the desired line, whereupon the operator at the office Z designates the toll switching trunk circuit over .which connection should be established. Assuming thetoll switching trunk circuit H to be that designated. the operator at the ofiice Z after designating this trunk circuit, inserts plug (it) of the toll switching trunk circuit H into jack ('51 of the telephone line Gr. Relay 62d and cut-off relay 63 thereupon operateover a circuit from battery through the winding of relay 62, sleeve contacts of the plug 60 and the ack 61 and the winding of cut-off relay 63 to ground. The energization of relay 62 causes supervisory lamp 64 to be lighted over a circuit from battery through the lamp 64, lower alternate contact of relay 62, resistance 65 and the normal contact of relay 66 to ground. The operation of the cut-off relay 63 disconnects the line relay 67 from the line wires of the telephone line Gr.

Connection 0f trunk line L with toll switching trunk circuit [I Winding of relay 58 to ground, and the latter .overa circuit from battery through the contact of relay 72, winding of slow-release relay 7 l and the normal contact of signal receiving relay 75 to ground. Relay 74,111 opcrating prepares a temporary holding circuit .for the signal receiving relay 75; the function of which will more fully hereinafter appear.

' The operation of relay 58opens the circuit of and extinguishes the supervisory lamp 5?.

In closing its upper alternate contact relay 58 causes the operation of su aervisory relays 56 and 66 over a circuit fromliattery through the left-hand winding of supervisory relay 66, left-hand normal contact of relay 76, tip contacts of the jack 71 and the plug 70, upper alternate contact of relay 58', upper normal contact, of ringing relay 77 winding of supervisory relay 56,2right-hand alternate contact of signal receiving relay 55, lower normal contact of ringing relay 77, ring contacts of the plug 70 and the jack 71, the right-hand normal contact of relay 7 6 and the right-hand \vindingeoi supervisory relay 66 to ground. Supervisory relay 66, in OPGIRtlH Q' OPGIIS the circuit of and extineuishes the supervisory lamp 64;

The energization of supervisory relay 56 causes the energization of slow-release relays 7 8 and 7 9 over a circuit battery through the Winding of these two relays in parallel and the alternate contact of supervisory relay 56 to ground. The opening of the lefthand normal contact of relay 78 causes the deenergization of a normally energized relay 24:, which then causes the operation of relays in N, K and M of the sending equipment SE. The operation of the relay M causes the energization of relay 24: over a' clrcuit'including slgnal control lead A Upon the energization of relay 24 it looks up over a circuit from battery through its winding, contact 34, alternate contact of relay .78 and alternate contact of the energized relay 79 to ground. At the time of the operation of relay :M? of the sending equipment SE, start relay36 and storing relay 4 thereof were operated, Storing relay t causes negative currentio be connected with the individual sendingsegment 4' of the sending distributor TD of the sending equipment SE. Upon the operation of the start relay 36 the sending distributor TD functions to transmit over the common signaling pathP, a starting positive impulse followed'by a code signal of 5 impulses the first, second, third and fifth of which are positive and the fourth negative. The storing relay 4, signal control relays KZM and N? andthe sending distributor TD and other control apparatus of the sending equipment SE, after the transmission of the code signal, is restored to normal condition,

Thetransmitted starting impulse and the cod signal bein receiv d at the oflice X, the differential polarized relay 40 cooperates with the receiving distributor RD, of the receiving equipment RE to select the signal receiving lead D and to transmit thereover a negative impulse which traverses the left-hand winding of and energizes the signalfreceivin'g relay 28. The signal receiving relay 28 upon'being energized locks up over a circuit from battery-through ts right-hand alternate contact and {righthand winding to ground. Following the energization of signal receiving relay 28, all

apparatus of the receiving equipment RE is restored to normal condition, ready to recelve any other transmitted code signals originating at the office Y. The energiza-' tion of this signal receiving relay 28 connects resistance 86 in parallel with the winding of relay 22, thereby loweringthe resistance of the circuit of supervisory lamp 23 to such an extent that the lamp becomes illuminated. 1 This lighted lamp now 'serves as a signal to the operator at the." oflice X,

indicating that the connection has been completed through'to theline of the wanted subscriber, and that the'established circuit is in condition for signaling the subscriber of the wanted line. The. opening of the normal contact of signal receiving relay 28 causes the deenergization of relay 26 which upon releasing its armature. connects the energizing winding of signal receiving relay 27 with the receiving conductor D Operator at oflice X aotuates ringing key.

,The operator at office 'X upon observing the lighted condition of the supervisory lamp 23 may actuate ringing key. 87 which connects the source of ringing current 88 with the, talking conductors of the cord circuit F and the trunk line L t; Relay 89 is operated by current from the source '88,

causing the energization of slow-release relay 35. The slow-release relay 35 in closing ing coil, which might affect apparatus con nected with the trunk linebeyond this repeating-coil. The opening of the normal contact of relay 85 causes the deenergization of the relay 24 in the manner previously described in connection with the insertion of the plug within the jack 21. The closure of the lower alternate contact of relay causes the energization of slow-release relay 91. Relays N K and M operate and lock up upon the deenergization of relay 24:. The operation of relay M causes the energization of relay 24 which thereupon locks up over a circuit from battery through the right-hand alternate contact of relay 22, winding of relay 24, contact 34: thereof and the left-hand contact of slow-release relay 91 to ground. The energization of this slow-release relay 91 also opens its righthand contact which disconnects resistance 86' from parallel relation with the Winding of relay 22, thereby increasing the resistance in circuit with the lamp 23 which then ceases to glow. Therefore during the operation of the ringing key 87 the supervisory lamp 28 is extinguished.

The operation of relay l 72 also causes the operation of storing relay 4. and starting relay 36 in the manner herei nbefore described. The sending distributor TD thereupon functions to transmit over the common signaling path P, a code signal o-f'five impulses, the first, second, third, and fifth of which are positive and the fourth negative. After the transmission of this code signal, the sending distributor TD, its control apparatus, storing relay 4: and control relays K M and N are restored to normal condition.

The code signal is received at the oflice Y causing the differential polarized relay 40 connected in the common signaling path P, and the receiving distributor RD controlled by and cooperating with the relay 10 to function in the manner hereinbefore described to select the signal receiving lead D and to transmit thereover a negative impulse. The receiving equipment is then restored to normal condition. This negative impulse transmitted over the signal receiving lead D traverses the left-hand winding of and energizes the signal receiving relay 75. The polarity of this impulse being the same as the original energizing impulse of receiving relay it' does not affect the condition of this signal receiving relay which therefore, remains locked up.

The signal receiving relay 75, upon ener- 'gization, completes a locking circuit from battery through the contact of relay 7 el and the left-hand alternate contact-and winding of signal receiving relay to ground. The closure of the left-hand alternate contact of signal receiving relay 7 5 causes the energization of slow-release relay 95, whereupon ringing relay 77 and slow-release relay 96 are immediately energized. The slow-release relay 96 in closingits alternate contact establishes a substitute holding circuit for relay 24 which may be traced from battery throughthe winding of relay 24: contact Mrthereof and the alternate contact of-relay 96 to ground. Signal receiving relay 7 5,upon energization, opens'the energizing circuit [of slow-release relay 74. so thatthis slow-release relay 74: immediately begins to release its armature. Upon thefull release 'of the armature ofslow release relay 74 the locking circuit of signal receiving relay 75 is opened, releasing this relay. Then upon the opening of the right-hand alternate contact of signal receiving relay 75 the energizing circuit of slow-release relay 95 is opened. The full release of the armature of relay 95 opens the energizing circuits of ringing relay 77 and slow-release relay 96.' 'Relay 96 wasm'ade slow in'releasing so that its alternate contact will not be opened until after the energization of supervisory relay 56 following the release of ringing relay 77 as will more fully appear in next but one succeeding paragraph. Relays 74 and 95 are made slow in releasing so as to prolong the length of time that the ringing relay 77 is energized, and therefore the length of "time that ringing current is connected with the incoming end of the trunk line L Upon the energization of ringing relay 77 as before described, the normal contacts of this relay are opened causing the release of supervisory relay 56, which causes the re lease of relays 78 and 79. Relay 24 is not deencrgized by the release of relays 56, 78 and 79 for its circuit is maintained at the closed alternate contact of relay 96. Relay 78 is made slow in releasing so that it will not release its armature during the short intervals that the alternate contact of super- "visory relay maybe opened whent-he called subscriber is rapidly opening and closing the switchhook contact, aswill more fully hereinafter appear. 1 Relay 79, however, releases its armature upon each opening of the alternate contact of relay 56, said relay -7 9 beingmade only slightly slow to release.

The closure of the upper alternate contact of relay 77 completes a holding circuit for relay 66 which may be traced from battery through the left-hand Winding of relay 66, left-hand normal contact of relay 76, tip contacts of-the' jack 71 and the plug 70, the upper alternate contact of relay 58 Hi l y and the up er alternate contact of ringing relay 77 to ground. The closure of the lower alternate contact of ringingrelay 77 causes the operation of ringing response relay 98'over a circuit from the source of ringing current 97 through the lower alternate contact of ringing relay 77, ring contacts ofthe plug'70 and the jack-71, windingof ringing response relay 98,'the condenser iii-series therewith, tip contacts of the jack 71 and the plug 7 ;v upper alternatecontact of relay 8 and the upper alternate contact of ringing relay? 7 to ground. Relay 98 in operating causes the operation of relay 76 and ringing relay 99-ove'r a circuit-from s batteryathroughlthe left-handwinding of operation looking relay 76, winding of relay 99. and the contact ofringing response 98 to ground; Re:

la 76 in o erating o ens the temporary Y P P holding circuit of relay 66 but before doing this establishes another holding circuit therefor which may be traced frombatter through the lett hand winding of relay 66 and-the alternatecontact of relay 76 to ground. Relay 76 in-openingl its normal contacts disconnects relay 66 from the talking conductorsvof the toll switching trunk circuit H while ringing current is connected] therewith. The energizatio-n-o'f ringing relay 99 connects the source of ringing current 100 with the telephone line G to cause the o-fithe usual call bell at the station. or

"wUpon the deenergization-of the ringing relay 77 in the manner hereinbefore described ringing-z current r is d1sconnected from the incoming end of the trunk line i L ,-whereupon relays 98, 76 and 99 release their armatures. .40

I The release of ringing relay 99d1sconnectsfr1ng1ng current from the call'ed line while 'th'e release of relay 76 in connection with the release of the ringing relay 77 causes the energization of supervisory relay'56, relay 66 being maintained energized over the circuit which energizes supervisory relay '56. The energi-zation of supervisory relay 56 causes the reenefrgization of relays 78 and. 79 in the manner hereinbefore described.

The energizing circuitiof relay 96 is opened at the same time as that otringing relay 77, but is made slow in releasing, so that the "holding or locking'circuit of relay 24 including the alternate contact of relay 96 is not opened until after another "holding or circuit vtherefor is established through the alternate contacts of relays 78 and'79. Relay 24 is thereforenotaifected when ringing on'the wanted line. I 0 26mm at 0 am X 'r'es'zforee ringing key.

I Upon the restoration of the ringing 'key 87 to normal position relay 89 deenergizes causing the release of slow release relay 35 which removes-the short-circuit of the leftlease relay v91.

releasing so as to insure that the locking :handwindings of the repeating coil 90 and opens the energizing circuit of slow-re- Relay '91 is made slow-in circuit of relay 2 1 will be maintained closed atthe left-handcontact of relay 91Quntil after closure of the normal contact of relay oez'ccr fromhswitcizghoolc. i

1 i The subscriberat the station on telephone lineG in responding to the operation of, the

call .bell therea't removes the receiverfrom the. switchhook thereby causing the operation of supervisory relay 105 over acircuit from battery through the winding of superv sory relay 105, upper normal contact of ringing relay '99,ringcontacts of the plug 60 and the jack 61, out over one side of the line, through the substation apparatus, and back over the other side iof'the line, tip

contactsof the jack 61 and the plug 60, upper alternate contact of relay 62' and-lower nor-mal contact of ringing relay '99 to ground. Supervisory relay 105' in operating causes the energization of relay 76 over a circuit from battery through :the left-hand WlIldlIlg of relay 7 6, contact of supervisory relay 105, right-hand-winding of relay 76 and the, alternate contact of relay 66 to groundb Relay-76 inroperating closes its alternate contact and opens itsIno-rmal contacts .whereby relay 66 is disconnected from the circuit includingthe supervisory relay 56, and is maintained energized through its left-hand winding and the, alternate contact of relay 76. 1 Relay 76- in operating also causes the deenergization of supervisory relay 56.' Relay 96 isnot now energized so that the deenergiz'ation of relay. 7 8 1501- lowing the 'deenergiz-ation of supervisory relay56 opens the locking circuit of red i lay- 241- which thereupon releases its armatures. I Battery is now connected with the signal control leads B and 0' extending to thesending equipment SE. I Relay N of'the sending equipmentYSE is ener ized vover the signal-control lead B and locks up causing the energization of relays M and I of sending "equipment SEC The venergization of relay M": in, addition to causingthe energization of start relay 36 and storing relay 1 also causesthe energizatlon 0t storing relay '5 of this sending equipment SE .whichis energizedthrough acontact of relay M and overthe leads C and right-hand normal contact of relay 78. Positive signaling/current is now connected with individual sending segments 1, 2 and 3' and negative signaling current with the individual sending segments 4 and 5 of the sending distributor TD of the sending equipment SE so that'a code signal of five impulses, the first three of which are positive and the last two negative is transmitted over the common signaling path P by the sending distributor TD. When the brush of the distributor associated with the sending equipment SE reaches its normal position after transmitting the code signal all apparatus associated with the sending equipment SE is restored to normal position and relay 2% is locked up.

The transmitted code signal being received at the oflice X causes the difierential polarized relay i0 and the receiving distributor RD of the receiving equipment to cooperate whereby the signal receiving lead D is selected by the first tour impulses of the code signal, and the fifth impulse of the code signal causes the energization and locking upof the pole changing locking relay 45. The relay 45 upon energizing cooperates with the receiving distributor RD to transmit a positive impulse over the selected signal receiving lead D which traverses the left-hand winding of signaling receiving relay 28 and the right-hand winding of signal receiving relay 27. The relation of the windings of the signal receiving relay 28 is such that upon the flow of positive current through its lett-hand winding, when it is locked up through its right-hand winding the relay is diiierentialized and releases its armatures. Signal receiving relays 27 and 28 are alike, so that the flow of positive current through its right-hand winding energizes the same but the closure of its locking circuit upon energization, causes this relay 27 to be diii'erentialized, and release its armatures. Receiving relay 28 in releasing its arniatures opens the circuit through resistance 86, thereby removing this resistance from parallel relation with the winding of relay 22, causing an increase in the resistance of the circuit of the supervisory lamp 23 which now ceases to glow. The closure of the normal contact of signal receiving relay 28 causes the energization of slow release relay 26 which opens its contact, disconnecting theenergizing winding of signal receiving relay 27 from the receiving conductor or lead D The extinguishment lot the supervisory lamp 23 serves as a signal to the operator indicating thatvthe called subscriber has answered.

It is to be observed that the apparatus at the office X is now in the same condition that it was following the transmission of the code signal over the signaling path P resulting from the origination oi the signal at this oflice by the inseition oi the plug 20 ot the cord circuit F into the jack 21 of the trunk tion.

line L Hence all relays at the oflice X are deenergized with the exception of relays 22, 24, 25 and 26 and relay 39 of the receiving equipment RE which corresponds to relay 39' of the receiving equipment located at the office Y.

At this time the following relays at the ofiice Y are energized: signal receiving relay 55, relays 72, 58, 24 and 74, and relay 39 associated with the receiver distributor RD, while at the office Z relays 62, 63, 66, 76 and 105 are energized.

Subscriber restores receiver to the switchhook.

At the conclusion of the conversation the subscriber at the station on telephone line G restores the receiver to the switchhook, whereupon supervisory relay 105 deenergizes, opening the circuit of and deenergizing relay 76. Relay 66 is thereupon c011- nected in circuit with supervisory relay 56 causing the energization of this supervisory relay '56 which closes the circuits of and energizes relays 7 8 and 79. Upon the opening of the left-hand normal contact of relay 78, relay 24 is deenergized connecting battery with signal receiving lead B The connection of battery with the signal control lead 13 causes the sending distributor TD of the sending equipment SE to transmit over the signal path P a code signal of five impulses, the first, second, third and fifth of which are positive and the fourth negative. Following the transmission of this code signal relay 24: is locked up in the manner before described and the apparatus of the sending equipment SE is restored to normal condi- This transmitted code signal is received at the ofiice X by the receiving equipment RE, which selects the signal receiving lead D and transmits thereover a negative impulse which traverses the left-hand winding of and energizes signal receiving relay 28. Signal receiving relay 28 locks up causing the release of slow-release relay 26 which connects the energizing winding of signal receiving relay 27 with the signal receiving lead D Signal receiving relay 28 in closing its left-hand alternate contact connects ground with the resistance 86, thereby including this resistance in parallel relation with the winding of relay 22. The supervisory lamp 23 is thereupon lighted to furnish disconnect signal to the operator at the office X.

Operator at ofiicc X disconnects (10rd circuit F from trunk Zine Z The operator at office X upon observing the lighted condition of the supervisory lamp 23 withdraws the plug 20 from the jack 21, causing the release of relays 22,

24 and 25. The deenergization. of relay 22 connects the battery with signal control lead C while the deenergization of relay 24 connects batter with the signal control lead B Relays I M and N then operate in the manner hereinbefore des ribed and upon the operation of relay M restoring lead A is normal contact of relay 22, winding of relay 24, contact 34 thereof and the normal contact of relay 85 to ground. The oper- ,ation of relay M also causes the. operation of start relay 36 and. storing relay 4 in the manner hereinbefore described and in addition causes the operation of storing relay over a circuit from battery through the left-hand normal contact of relay 22,. signal control lead. C middle alternate contact of relay l and the winding of storing relay5to ground.

' The sending distributor TD thereupon functions to transmit, over the slgnaling path P a ode signal comprising three positive impulses followed by two nagative impulses; This code signal being received at the 'ofiice Y, the differential polarized relay 40 and the receiving distributor RD cooperate to cause the selectionof signal receiving lead D and the energization and locking up of relay '45 which cooperates with the'receiving distributor-RD to'transmit a positiveimpulse over the selected signal receiving lead D. This positive impulse traverses the left-hand winding of "The closure of the "normal contact of signal receiving relay causes supervisory lamp 557 to be lighted over a circuit from battery through the lamp .57, lower alternate contact of relay 58 and the'normal contact of signal receiving relay 55to ground. Slow-release relay 110 is also energizedover a ircuit from'battery through the middle alternate contact of relay 58, winding of relay 110 and the normal contact of signal receiving relay 55 to ground. Relay 110 thereupon opens its contact, disconnecting the energizing" winding of signal receiving relay from the signal receiving lead D. This relay 110 is provided and is made slow in releasing; so that if the plug 70 is inserted in the jack 71 before the plug 26 is inserted in the ack2l, relay 110 will be energized, to prevent the false operation I grounded to energize relay 24- which then locks up through the right-hand of signal receiving relay '75, when the first negative impulse is transmittedyover signal receiving lead D d ue to the insertion of theplug '20 in the jack21.v The release of "relay 66 causes supervisory lamp 64 to be lighted over a circuit from battery through the lamp 64, lower alternate contact of relay 62, resistance 65 and the normal contact of'relay 66 to ground, The supervisory lamps 57 and 64 in lighting at' the oflices- Y' and Z respectively. 1

Upon thedeenergization of supervisory.

serve as disconnect signals to the operators relay 56 fol-lowing'the release of signal receiving relay 55 in the manner previously describech relays 78 and 79 releasetheir locks up. The sending distributor TD."

ransmits over the common signaling. path P a code signal consisting of three positive impulses followed by two negative impulses.

This code signal being received by the receiving equipment RE at the oificeX, se-

lects the signal receiving lead D and transmite thereover a positive impulse which traverses the left-hand winding of; and energizes the signal receiving relay 28. Signal receiving relay 28 is at this time locked up so that this positive impulse through its left-hand winding renders the relay differential and it releases its armatures, whereupon all apparatus at the office is re stored tofits normal condition the only energized', relays beingrelay 24, and relay 39 of the receiving RE. p v I The operators at the offices Y and Z upon observing the lighted, conditionof the respective supervisory lamps 57 and 64 withdraw the plugs 70 and 60. from the respectivejacks 71 and 61, therebyrestoring all apparatus at these two offices tonormal condition. At this time the only energized relays at the office Y are relays 24 and 39,

while there are no energized relays at the office Z.

1 calls operator at 'ofiice X;

Should thesubscriber at the station on, the

telephone line G, after answering a. call when conneotlon is established between the toll cord circuit F and the telephone line G. by way of trunk line L and the toll switching trunk circuit H, wish to signal the operator at the ofiice X, this may be done by repeatedly opening andclosing the switchhook contact at the stationon telephone line Gr. The first. opening of the switchhook con tact causes the sending distributor TD of windings of the signal receivin connected with individual sending segments 1, 2 and 3 and negative signaling current with the individual sending segments 4: and 5 of the sending distributor TD with the sendingequipment SE is restored to normal position and relay 24' is locked up.

The transmitted code signal being received at the ofiice X causes the differential polarized relay and the receiving distributor RD of the receiving equipment to cooperate whereby the signal receiving. lead D is selected by the first tour impulses of the code signal, and the fifth impulse of the code signal causes the energization and locking up of the pole changing locking relay 45. The relay upon energizing cooperates with the receiving distributor B D to transmit a positive impulse over the selected signal receiving lead D which traverses the left-hand winding of signaling receiving relay 28 and the right-hand winding of signal receiving relay 27. The relation of the relay 28 is such that upon the flow of positive current through its left-hand winding, when it is locked up through its right-hand winding the relay is difi'erentialized and releases its armatures. Signal receiving relays 27 and 28 are alike, so that the flow of positive current through its-right-hand winding energizes the same but the closure of its looking circuit upon energization, causes this relay 27 to be difi'e-rentialized, and release its armatures. Receiving relay 28 in releasing its armatures opens the circuit through resistance 86, thereby removing this resistance from parallel relation with the winding of relay 22. causing an increase in the resistance of the circuit of the supervisory lamp 255 which now ceases to glow. The closure of the normal contact of signal receiving relay 98 causes the energization of slow release relay 26 which opens its contact, disconnecting the energizing winding of signal receiving relay 27 from the receiving conductor or lead D The extinguishment of the supervisory lamp 23 serves as a signal to the operator indicating that the called subscriber has answered.

It is to be observed that the apparatus at the ofiice is now in the same condition that it was following the transmission of the code signal over the signaling path P resulting from the origination of the signal at this o'fiice by the insertion of the plug 20 of the cord circuit F into the ack 21 of the trunk line L Hence all relays at the office X are deenergized with the exception of relays 22, A l, 25 and 26 and relay 39 of the receiving equipment RE which corresponds to re-' lay 39 of the receiving equipment located at theofiice Y.

At this time the following relays at the office Y are energized: signal receiving relay 55, relays72, 58, 24 and. 74;, and relay 39 associated with the receiver distributor RD, while at the oflice Z relays 62, 63, 66, 7 6 and 105 are energized.

Subscriber restores'receioer t0 the switchhook.

At the conclusion of the conversation the subscriber at the station on telephone line G restores the receiver to the switchhook, whereupon supervisory relay 105 deenergizes, opening the circuit of and deenergizmg relay 76. Relay 66 is thereupon connected in circuit with supervisory relay 56 causing the energization of this supervisory relay 56 which closes the circuits of and energizes relays 7 8 and 7 9.- Upon the opening of the left-hand normal contact of relay 78, relay 24 is deenergized connecting battery with signal receiving lead B The connection of battery with the signal control lead B causes the sending distributor TD of thesending equipment SE" to transmit over the signal path P a code signal of five impulses, the first, second, third and fifth of which are positive and the fourth negative. Following the transmission of this code signal relay 24: is locked up in the manner before described and the apparatus of the sending equipment SE is restored to normal condition.

This transmitted code signal is received at the ofiice X by the receiving equipment RE, which selects the signal receiving lead D and transmits thereover a negative impulse which traverses the left-hand winding of and energizes signalreceiving relay 28. Signal receiving relay 28 locks up causing the release of. slow-release relay 26 which connects the energizing winding of signal re ceiving relay 97 with the signal receiving lead D Signal receiving relay 28 in closing its left-hand alternate contact connects ground With the resistance 86, thereby including this resistance in parallel relation with the winding of relay 22. The supervisory lamp 23 is thereupon lighted to furnish disconnect signal to the operator at the office X.

Opera-for at ofice X disconnects (10rd circuit F from trunk Zinc L The operator at office X upon observing the lighted condition of the supervisory lamp 23 withdraws the plug 20 from the jack 21, causing the release of relays 22,

24: and 25; The deenergizationof relay 22 connects the battery with signal control lead C while the deenergization of relay 24=connects batter with the signal control lead B Relays 1x M and N then operate in the manner'hereinbefore des ribed and left-handnormal contact of relay 22, signal control lead C middle alternate con tact of relay M and the Winding of, storing relay 5 to ground.

Thesending distributor TD thereupon functions to transmit over 'the'signaling path .P. a code signal comprising three positive impulses followed by twonagative impulses. This code signal being received at the office Y, the diiferential-polarized relay 40 .and the receiving distributor RD cooperate to cause the selection of signal receiving lead D? and the energization and locking up of relay l5 which cooperates with the receiving distributor RD to transmit a positive impulse'over the selected signal recelving lead .D J- This positive 1mpulse trave ses the left-hand winding of signal receiving relay which isthereby difl'rentialized and-releases its armatures. This "positive impulse traverses the right.- hand winding of and energizes signal receiving relay 75, but this relay is immediately diiferentialized by'the closure of its left-hand contact and releases its armatures. The opening of the right-hand alternate contact of signal receiving relay 55 opens the ci cuit of supervision relays 56 and 66 which thereupon release their armatures. The closure of the normal contact of signal receiving relay '55 causes supervisory lamp 57 to he lighted. over a circuit from battery through the lamp 57, lower alternate contact of relay 58 and the normal contact of signal receiving relay 55 to ground. Slow-release relay 110 is also energized over a ircuit from battery through the middle alternate contact'of relay 58, winding of relay 110 and the norinal contactbfsignal receiving relay 55 to ground. 1 Relay 110 thereupon opens its contact, disconnecting the energizing winding of signal receiving relay 75 from the signal receiving lead D. This relay 110 is provided and is made slow in releasing. so that if the plug 70 is inserted in the jack 71 before the plug,

26 is inserted in] the ack 21, relay 110 will be energized, to prevent the false operation of signal receiving relay 75, when the first negative impulse is transmitted over 'signal receiving lead D due to the insertion of the plilg. 20. in the jack 21. The release of relay 66 causes supervisory lamp 64 to be lighted over a circuit from battery through the lamp 64:, lower alternate contact of relay 62, resistance 65 and the normal contact of relay 66 toground. The

tery'to signal control lead While relay 78 connects battery to signal control lead C The sending equipment 'SE. thereupon functions to groundthe restoring lead A energizing relay 24 which thereupon locks up; The sending" distributor TD transmits over the common signaling path P a code signal consisting of three positive impulses followed'by two negative impulses.

This code signal being received by the receiving equipment RE at theoflice X, selects the signal receiving lead D and transmits thereover a positive impulse which traverses the left-hand winding of and energizes the signalv receiving relay 28.- Signal receiving relay 28 is at this timelocked up so that this positive impulse through its left-hand'winding renders the relay differential and it releases its armatures, whereupon all apparatus at the office X is restored to its normal condition, the only err fergized relays being relay 24;, and relay 89 of the receiving RE.

' The operators at the offices Y and Z upon observing the l ghted condition of the respective supervisory lamps 57 and 64: withdraw the plugs 70' and 60 from the respective jacks 71'and 61, thereby restoring all apparatus at these two ofiices to normal condition. At this time the only energized relays at the ofiiceY are relays 24/ and 39,

while there are no energized relays at the office V v i Subsmdberat station: on telephone Zine (7 recalls operator at oflice X.

Should the subscriber at the station on the telephone line G, after answering a" call when connection is established between the toll cord circuit F and theitelephone line G by way of trunk line L and the toll switching trunk circuit H, wish to signal the repeatedly opening and closing the switchh'ook contact at the station on telephone line Z operator at theoflice X, this may be done by the sending equipment SE to transmit over the signaling path P a code signal of five impulses the first three of which are positive, the fourth negative and fifth positive. This code signal being received at the ofiice X, receiving equipment RE causes a negative impulse to'be transmitted over the signal receiving conductor D Signal receiving relay 28 thereupon energizesand locks up. The energization of signal receiving relay 28 causes the deenergization of relay26 and the lighting of lamp 23. In connection with the transmission of this code signal it will be recalled that supervisory relay 56 was energized by the opening of the switchhook contact and upon being energized caused the energization of relays 7 8 and 79. When recalling the operator at the office X the subscriber at the station on te ephone line G rapidly opens and closes the switchhook contact. The speed of opening and closing this contact is such that supervisory relay 56 is energized upon each opening and deenergized upon each closure of this switchhook contact. Relay 79, which is only slight-- ly slow in re easing and faster than relay 78, is energized upon each energization of supervisory relay 56 and is deenergized upon each deenergization thereof, but relay 78 is slower in releasing so that during the short interval that supervisory relay 56 may be deenergized by the closure of the switchhook contact during the time the subscriber is rapidly opening and closing this contact, relay 78 maintains its normal contacts open and its alternate contact closed thus preventing the application of battery to the disconnect lead 0' -Upon the first closure of the switchhook contact following the opening thereof, relay 79 releases its armature, but the contact of relay 79 is not opened until after the closure of the normal contact of supervisory relay 56 whereby relay 24f remains locked up. The normal contact of supervisory relay 56 therefore controls relay 24 while the subscriber is rapidly opening and closing the switchhook contact to recall the operator at the office X. Upon .each subsequent opening of the switchhook contact and consequent energization of relay 56 while the subscriber is rapidly opening and closingthis contact, relay24 is deenergized, before relay 7 9 can respond to the closure of the alternate contact of relay 56, to cause the sending distributor TD to transmit a code signal of five impulses the first three being positive, the fourth negative and the fifth positive. Each such subsequently transmitted code signal being received at the oflice X causes the receiving equipment RE -to select signal receiving-lead D and to transmit thereo-ver a negative impu se which energizes signal receiving relay 27. This signal'receiving relay then locks up over a circuit from battery through the contact of slow release relay 25 and the left-hand contact and winding of signal receiving relay 27 to ground. Slow-release relay 29v is energized upon the energization and locking up of signal receiving relay 27 and disconnects ground from the resistance 86' and connects therewith grounded interrupter 111, so that the resistance 86 is intermittently connected in parallel with the winding of relay 22. Supervisory lamp23 is thereupon intermittently lighted to furnish a signal tothe operator-at the office X, indicating that the subscriber at the station on telephone line G is signaling.

Upon the opening of the normal contact-of signal receiving relay 27, due to the energization thereof, relay 25 begins to release, and when its armature is fully released the locking winding of signal receiving relay 27 is opened, so that this relay releases its armatures, opening the energizing circuit of slowrelease' relay29. The speed at which the switchhook contact at the station on telephone line G is being opened and closed is such that another negative impulse is received over the signal receiving conductor D before slow release relay 29 can open its alternate contact, whereby signal receiving relay 27 is again energized and upon being energized immediately reestablishes the energizing circuit ofv slow-release relay 29. Therefore, by making relays 25 and 29 slowreleasing the interrupter 111 is maintained in operative relation to the resistance 86 so long as the subscriber at the station on telephone line G is rapidly opening and closing the switchhook contact to signal the operator at the ofiice X. After repeatedly and rapidly opening and closing the switchhook contact to signal the operator, the subscriber ceases such operation, leaving the switchhook contact closed, whereby supervisory relay 105 and relay 76 operate to cause the deenergization of supervisory relay 56. Upon the deenergization of this relay 56, relays 78 and 79 release their armatures, causing the deenergization of relay 24'. Relay 78 being deenergized, battery is now connected with signal control'leads B'2 and C2, and the sending distributor .TD of the sending equipment SE therefore transmits over the signaling path P a code signal of five impulses of which the first, second, third and fifth are positive and the fourth negative which upon being received at the ofiice X causes the receiving equipment RE to select the signal receiving lead D and to transmit a positive impulse thereover. This positive impulse traverses the left-hand winding of signal receiving relay 28 causing the relay to be differentialized. and it' thereupon releases its armatures, disconnecting the intermittent ground from the resistance 86. The supervisory lamp 23 therefore ceases to glow.

Had the subscriber ceased the rapid opening and-closing of switchhook contact by leaving the switchhook contact open, then no further code signals would be transmitted from the office Y over the signaling path P. Consequently slow releasev relay. 29 would fully release its armature, substituting a continuous for. the intermittent: ground,

thereby'causing the supervisory lamp 23 to becontinuouslylighted to furnish a discon- -nect signal to'the operator at the office X.

another code signal would be transmitted, the same as in the case when the subscriber first answers the call, to permanently extinguish said lamp since the relay 27 is not operated to cause'the interrupter 111 to reiipeatedly flash the lamp unless the switchhook contacts are again opened within a predetermined period of time after-the first openingthereofl In this manner, the operation of repeatedly flashing the: lamp 23 is delayednuntil successive code signals are 'received to operateboth relays 27 and 28. I

" Theoperations described abovekwithreference to building up a'connection with telephone'line G over the trunk line L? and the breaking down-of such .a connection are characterlstic of those taking place 1n building up and breaking'down a connection over any one of the trunk linesto which the sig 'naling path Puiscommon. The only essentialdifi'erence in operation, so far as the establishment-of connections over the different trunk lines is concerned, is that different code signals are employed for the different trunk lines, and diflierent sets of relays K, M'and N will-be operated andthe storing relays *will be operated in 'difieringcombinations to determine polaritiesconn'ected with the individual sendin segments of the sending distributors an the lockingv relays. and

rpyramid selecting relays controlled on the receiving distributors will be operated in differing combinations to select the appropriate signal receiving leads-and thefsignal associated therewith to be operated. '"While this invention is not limited to any particular arrangement of codesignals, the codes'sho wn in the following table'haverbeen found to be very satisfactory fora total of sixteen trunk lines served by the same common signaling path. In this table, the numbers in the first column indicate the numbers assigned to the trunk lines,iwhile the numbers in the remaining columns indicate' the order of the negative impulses in" each groupof five. The

number O -appea-ring in the first line in the second, third, fifth and seventh columns 'Whatis' claimed of the table means that no negative impulses are transmltted.

Signals from ofiice X to Signals from ofiice Y to 7 office Y. office X.

Ti'unkline 1 v i Y 15- ce'iver eceiver i as Guard? connect on on hook, ing.

1. 0 O i 5 1 0 l 5 2.. 4 4. 45 4 45. 3.. 3 r 3 3s i a 35 4.. 1'2 2 25 2 25 5. l 1 l5 1 15 .34 34 345 34 345 7. 24 24 245 v 245 8.. 14 14 145 14 145 ,9.. 23 23 .235 23- 235 10. 13 13 135 13 135 11... 12. 12 125 2 12 i 125 12 234 v 234 2345 234 2345 13.. 134 134 1345 134 .1345 14. 124 124 1245,. 124 1245 15 123'. 123 1235' 123, 1235 16 1234 1234 12345 1234 12345 1. In a telephone system, in combination, a plurality OfiftTflIlSIlliSSlOll0113011118 and a signaling path comn'ion-thereto extending between two stations, a signaling device at one station associated with a predetermined one ot the transmission circuits,

means at the other station 7 responsive {to rapid changes-in the conditioniof the pre-' determined transmission circuit to transmit a succession of signals over the signaling path, signal receiving relay 'at the one station responsive to the first transmitted signal, a second receiving relay thereat responsive to each subsequently transmitted signal, a holding circuit for-the second signal receiving relay established upon each response thereof, andineans controlled by the second signal receiving relay for causing theoperation of the'signaling device.

H 2. In. a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, a signalingdevice at one station associated with a predetermined vone of the transmission circuits, means at the other station responsive to rapid changes in the condition of the predetermined trans-- mission. circuit totransmit a succession of signals over the signalingpath, a signal receiving relay at the one station responsive to the first transmitted signal, a second receivingrelay thereat responsive to each subsequently transmitted signal, a holding circuit for the second signal receiving relay established upon each response thereof, interrupter mechanism, and means controlled bythe second signal receiving relay for coi'inecting .the interrupter mechanism in operative relation to the signaling device.

3. In a telephone systen1,-in combination,

a plurality'oi' transmission circuits and a signaling path common thereto extending between two stations, a signaling "device at .oneistation associated withia predetermined ceiving relay thereat responsive to each subsequently transmitted signal, a holdingcircuit for the second signal receiving relay established upon each response thereof, interrupter mechanism, and a relay energized upon the response of the second, signal re ceiving relay to connect the interrupter mechanism in operative relation to the sign-v naling device and to maintain such, operative relation after the deenergization of the second receiving relay.

4. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, a signaling device at one station associated with a predetermined one of the transmission circuits, means at the other station responsive to rapid changes in the condition of the predetermined transmission circuit to transmit a succession of signals over the signaling path, a signal receiving circuit at the one station, a signal receiving relay controlled over the signal receiving circuit and energized in response to the first transmitted signal, a local relay responsive to the energization of the signal receiving relay, a second signal receiving relay connected with the signal receiving circuit by the response of the local relay and energized in response to the next transmitted signal to cause the operation of the signaling device. I g a 5. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations,-a signaling device at one station associated with a predetermined one of the transmission circuits, means at the other station responsive to rapid changes in the condition of the predetermined transmission circuit to transmit a succession of signals over the signaling path, a signal receiving circuit at the one station, asignal receiving relay controlled over the signal receiving circuit and energized response to the first transmitted signal, alocal relay responsive to the energization of the signal receiving relay, a second signal receiving relay connected with the signal receiving circuit by the response of the local relay and energized in response to the next transmitted signalto cause the operation of the signaling device, interrupter mechanism. and means controlled by the second signal receiving relay and cooperating with the first signal receiving relay to cause the intermittent operation of the signalingdevice.

' 6. Ina telephone system, in combination,

a plurality of transmission circuits and a signaling path common thereto extending between two stations, a signaling device at one station associated with a predetermined one of the transmission circuits, 'means at the other station responsive to rapid changes in the condition of the predetermined t'ransmission circuit to transmit a succession of signals over the signaling path, a signal receiving circuit at the one station, a signal receiving relay having an energizing Winding permanently connected with the signal receiving circuit and controlled thereover and energized in response to the first transmitted signal, and a second signal receiving relay connected with the signal receiving circuit by the energization of the first sig nal receiving relay and responsive to the next transmitted signal to cause the operation of the signaling device.

7. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, a signaling device at one station associated with a predetermined one of the transmission circuits, means at the other station responsiveto rapid changes in the condition of the predetermined transmission circuitv to transmit a succession of signals over the signaling path, a signal receiving circuit at the one station and a signal receiving relay having an energizing winding normally connected with the signal receiving circuit and controlled thereover and energized in response to the first transmitted signal, a second signal receiving relay connected with the signal receiving circuit by the energization of the first signal receiving relay and responsive to the next transmitted signal to cause the operation of the signaling device, interrupter mecha:

nism, and. means controlled bythe second signalreceivingrelay and cooperating with the first signal receiving relay to connect the interrupter mechanism in operative relation to the signaling device.

8. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, a signaling device. at one station associated with a predetermined one of the. transmission circuits, means at the other station responsive to changes in the condition of the predetermined circuit to transmitsignals over the signaling path, a signal receiving circuit at the one station, a signalreceiving relay having an energizing and a locking winding, means responsive to the first transmitted signal for causing currentof one polarity to traverse the energizing winding, a circuit including the locking Winding established upon the energization of-the signal receiving relay, and means responsive. to asubsequently transmitted signal for causing current of the opposite polarityto traverse the energizing winding of the signal receiving relay, where b the signal receiving relay is deenergized.

"9. Ina telephone system, in combination,

a pluralityof transmission circuits and a signaling path commonthereto extending between two stations, a signal device atone station associated with a predeterminedone of the transmission; circuits, means at the other station responsive to changes in the condition of the predetermined transmission circuits to transmit'signals overt-he signaling path, a signal receiving relay at the one station'responsive to the first transmitted signal, a locking circuit therefor established upon the energization oithe signal receiving relay, a second signal receiving relay at the one station responsive to asubsequent ly transmitted signal, the locking circuitof the first named signal receiving relay being unaffected by the response of the second signal receiving relay, a locking circuit for the second signal receiving relay established upon the eiiergization thereof, and an operating'circuit for the signaling device controlled by the second signal receiving relay and including a contact of thefirst'signal receiving relay.

path, a signal receiving relay at the other station energized in response to the: transmitted signaha locking circuit'for the'signal receiving relay established upon the energization thereof, a, ringing relay controlled by and energized upon the respo'nseof this signal receiving relay, and athird relay controlled by-and controlling the locking circuit of the signalreceiving relay tocause the energization of the ringing relay for a predetermined period. i l

1 1. In a telephone system, injcombination, aiplurality of transmission circuits'iand a signaling path common thereto extending between two stations, means at one station responsive to a change inthe conditionof a predetermined one of the transmission circuits to-transmit a signal over the signaling path, a" signal receiving relay at the other station energized in response to the transnal .receiving relay established upon the energization thereof, a slow release relay energized responsive to the energization of the signal receiving relay, a ringing "relay energized upon the response o'ifthe slow release relay, and a fourth relay whose energizing circuit is controlled by the signal receiving relay controlling the locking circuit thereof and cooperating with theslow' re lease relay to Vdet'e'rminethe duration of the energization ofthe ringing relay. I

12. In a telephone systeirnin combination, a plurality of transmission circuits and a signaling path common thereto extending between two'stations, means at one station responsive to each change'in the condition of a predetermined one'of the transmission cir-.

cuits to transmit asignal over-"the signaling" i path, a signal receiving circuit attlie other station, a signal receiving relaythereat hav ing an energized winding normally connected with thefreceiviiig circuit, meansresponsive to a transmitted signal to cause current ofone polarity to traverse theenergizing winding of the signal receiving relay, a

locking circuit therefor established'upon the v energzation thereof, means at said other 'station responsive to a "'subse('1nently transmitted signal to cause current of the opposite polarityto traverse the energizing wind ing of the signal receiving relay to cause the ,deenergization thereof, an extension circuit atsaid other station, and a signaling device thereat' operatedvuponjthe energization of the signal receiving relay before the -prede-' termined transmission" circuit is connected Withthe extension circuit and again operated upon the deenergization of the signal receiving relay after the connectionof the transmission circuit with the extension circuit. 'f 1 13, In telephone system, in combination, a plurality oftransmissioii circuits" and a signaling path common thereto extending between two stations, means at one stationfor transmitting over ;the signaling path code signals individual to the different transmission circuits, a set of relays at the one station for each transmission line com prising a first relay for determining the code of the signal ftofbe transmitted, a second relay "for determining the order in which the code determining relays are energized, and a third relay controlling the energ zation of "the first and second relays or this set, and

means controlled, the third relay for preventing the simultaneous operation of two orderdetermining relays, I i y I 14. In a telephone system, in combination, a plurality of transmission circuits, a signaling path common thereto extendingbetween two stations, means atone station for transmitting overthe signaling path code I signals individual "tothe different transmismitted signal, a locking circuit for the sigsion circuits, a set of relays at the one station individual to each transmission circuit comprising a first relay for determining the code of the signal to be transmitted, a second relay for determining the order in which the--coded signals are transmitted,-and "a thirdrelay for-preventing the simultaneous transmission of two signals. v

15. In atelephone ysrem, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, means at one station for transmitting over the signaling path code signals individual to the different transmission circuits, a set of relays at the one station individual to each transmission circuit comprising a relay for determining the code of the signal to be transmitted, a relay for determining the order in which the code determining relays are energized, and a relay controlled by a change in the condition of its associated transmission line, and energizing circuits for the first and secondmentioned relays controlled by the third.

16. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, means at one station for transmitting over the signaling path code signals individual to the difierent transmission circuits, a set of relays individual to each transmission circuit located at the one station comprising a relay for determining the code of the signal to be transmitted, a relay for determining the order in which the code-determining relays are energized and a third relay energized in response to a change in the condition of its associated transmission line, and an energizing circuit for the third relay of one set controlled by an order-determining relay of another set.

17. In a telephone system, in combination, a plurality of transmission circuits and a signaling path common thereto extending between two stations, means at one station for transmitting over the signaling path code signals individual to the different transmission circuits, a set of relays individual to each of several of said transmission circuits comprising a relay for determining the code of the signal to be transmitted, a relay for determining the order in which the code determining relays are energized, and a relay responsive to achangein the condition of the transmission circuit to which it is individual and a circuit for each order-determining relay including contacts of a third-mentioned relay in another set.

18. The method wherein an operators signal is operated when a subscriber recalls which comprises delaying the operation of said recall signal until a predetermined time interval after the first operation of the switchhook for recall purposes.

19. In a telephone system, the combination with a recall control circuit, a signal controlled thereby and means for closing said circuit, of means for delaying the operation of the recall signal a predetermined time interval after the closure of said circuit.

20. In a signaling system, a plurality of transmission lines, a signal path common thereto, a signaling device, means responsive to a change in the condition of one of said lines for operating said signaling device and means for intermittently operating said signaling device only in response to more than one change in the condition of said line occurring within a predetermined period of time.

21. In a signaling system, a plurality of transmission lines, a signaling path common thereto, a signaling device, means responsive to a change in the condition of one of said lines for operating said signaling device, an interrupter mechanism for intermittently operating said signaling de vice and means responsive only to more than one change in the condition of said lines occurring within a predetermined period of time for rendering operative said interrupter mechanism.

In witness whereof, I hereunto subscribe my name this 16th day of July, A. D. 1919.

WILLIAM L. DODGE.

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