US908926A - Three-wire telephone system. - Google Patents

Description

o. WINSTON.

THREE WIRE TELEPHONE SYSTEM.

APPLICATION FILED MAR. 12, 1906.

Patented Jan. V5, 1909.

@im mgl-5 j UNITED STATES' PATENT GFFICE. CHARLES s. wnvsron, or CHICAGO, ILLINOIS, sseivo To KELLOGG SwI'roHnoARn a SUPPLY COMPANY, or CHICAGO, ILLINOIS, A CORPORATION or ILLINOIS.

Specification of Letters` Patent. i

'Patented Jan. 5, 1909.

Application filed March 12, 1906. Serial No. 305,435.

l To all whom 'it 'may concern:

, telephone systems of the three-wire' type as distinguished from systems employing only two conductors in the mulit le switchboard section of the lines. ln suci two-wire systems it is necessary to use a art of the talking circuit for the purpose o testing the idle or busy condition of the lines', and for signal ing purposes between the substations andthe central office. In three-wire systems an additional conductor is. provided for testing and signaling purposes, vso that these func-- tions may be performed entirely independent of the talking circuit. i

'Ihe objects of niy invention are to provide a system of the latter class that will be simple in Operation and inexpensive to install and one that will be free from possible voice current shunts other than those necessary to furnish the energy to the-lines for conversation, and from impedance in the talking circuit, whereby a high degree of efficiency is obtained.

My invention is illustrated in the accompanying drawing in which the ligure is a diagram showing twosubscribers lines and a l central oiiice equipment for connecting the lines for conversation.

Referring to the drawing, two subscribers stations 1 and 2 are shown connected with the central oifice'by means of line conductors 3` and 4. I have indicated a common battery substation outfit at the subscribers stations Consisting of the call bell 5 and condenser 6 in a permanent bridgeof theline conductors, and a transmitter 7 and receiver 8 yin a bridge of Said conductors normally open atthe switch hook 9.

At the central oflice the limbs of the telephone lines terminate in the windings 10 and 11 of a line relay 12, the winding 10 being connected with the non-grounded pole of the central olice battery 13 by-means of conductors 14: and 15, and the coil 11 being connected to ground through the conductor 16 and the normallyeclosed contacts 17 of the y cutoff relay 1S. A line lamp 19 is connected between the conductor 15 and ground through normally-open contacts of the line relay 12 and the normally-closed contacts 20 of the cut-off relay 18. The winding ofthe cut-oiil relay is connected between ground and the testing terminal 21 of the answering jack, said terminal and the tip and sleeve springs 22 and 23 of the jacks being multipled at the dilierent sections of theswitchboard.

The operators cord circuit consists of a tip strand 24 having an interposed, condenser 25 and a sleeve strand 26 having an interposed condenser 27. A Supervisory signal 28 is provided for the answering side Ofthe cord circuit, said signal being connected with the opposite poles of the battery 13 by means of conductors 29 and 30, and having the continuity of its circuit normally 'open at the front contact ofy supervisory relay 31 and normally closed at the lback contact of the supervisory relay 32. The relay 31 is connected between the non-grounded side of the battery 13 and the tllird contact of the plug by means of a conductory 33 and relay 32 is connected between the grounded pole of said battery and the sleeve strand of the cord circuit. A supervisory signal 34 is similarly connected with reference to battery 13 u on the opposite side of the cord circuit and Ihas the continuity of its circuit similarly con--` trolled by the normally-open contacts Of a supervisory relay 35, and the normally-closed contacts of a supervisory relay 36. The relay 35 has one side of its Winding connected with the non-grounded pole of battery 13, the othei` side thereof being connectedto the third contact of the callingr plug by conductor 37, and the relay 36 is connected between the grounded Side of the battery 1.3 and the sleeve Strand of the cord circuit. A' second pair ofnormally-closed contacts 38. are provided for the su ervisory relay 35, the conv tact anvil of sai pair being connected with the tertiary winding 39 ol the operators 1nduction coil by means of conductor 40. The

operation of the supervisoryrelay 35 seversv the connection between the ti strand and the tertiary Winding, and unites the normally-severed tip strand of the cord circuit at the front contacts of said relay for conversation. Y

A listening key 40 is provided adapted bridge the operators telephone .across the cord circuit in the usual manner; the transmitter 41 and the primary of the operator's induction coil 42may be supplied with current by the battery' 13 or from anu Atable source. A. ringing generator 43 is adapted to be connected with the limbs of the telephone line by means of a ringing key44 for the purpose of signaling the desired subscriber.

1n the operation of the system the subscriber at station 1, desiring to attract the attention of the operator, will remove his receiver from the switch hook and close a path for current from the battery 1 3 over conductors 14 and 15, the winding 10 of the line relay 12, limbs 3 and 4 of the telephone line including the substation apparatus, winding 11 of the line relay, conductor 16 and contact 17of the cut-oltrelay 18 kto ground. 'lhe line relay will attract its armature, closing the circuit of the line signal 19 from conductor 15 to groundl through the normallyclosed contacts 20 of the cutoft1 relay. Upon noticing the signal the operator will raise the plug of the cord circuit and insert the same 1n the answering jack of the calling line. Upon the insertion of the plug a path for current will be closed through the winding of the supervisory relay 31, conductor 33, testing terminal 21, and the winding of the cut-ori' relay to ground. Both relays in this path will be energized, the cut-ofirelay opening the circuit of the line lam 19 at its normally-closed contacts 20 an removing the round connection from the sleeve side of the ine at its normally-closed contacts 17. 'lhe relay 31 will close the circuit of the supervisory signal 28 at the normally-open contacts of said relay. lhe supervisory signal 28 would not be lighted, however, due to the energization of the supervisory relay 32 inresponse to a ow of current over the telephone line; this flow of current may. be traced from the battery 13 over conductors 14 and 15, winding 10 of the line relay, line, conductor 3, the substation apparatus, line conductor 4, sleeve spring 23 of the jack and the corresponding plug contact, sleeve strand 26 of the cord circuit, and the winding of said relayl to batter It will be seen, therefore,

that the signa 28 will remain dark-duringconversation, due to the fact that the circuit of said signal is jointly controlled by the relays 31 and 32, the former over a path local to the central olice, and the latter over a ath including the substation apparatus and epending for its operation upon the position of the subscribers telephone receiver. Upon moving her listening key 40 and bridging her telephone set across the cord circuit the o erator would be in communication with t e calling subscriber. Upon learning the number of the line wanted its conditionwould be tested in theusual manner by touching the tip of the plug to the testing terminal of the line wanted.` If a connection existed with the line at another position of the switchboard. the testing terminals throughout the multiple of that line would be raised to a potential above that of ground, due to the flow of current through the terminal at said position, 'to operate the cut-0E relay. Upon touching the ti of her plug to a multiple testing termina of a 'busy line a flow of current would result from the test rin over the tip strand of the cord circuit, conductor 40, through the tertiary winding 39 of the operators induction coil to ground. This flow of current would produce an inductive click in the operatorshead receiver, notifying her of the busy condition of the line. lfinding the line idle the o erator would insert the plug in `the jack of t e line wanted. On the insertion of the plug current would ow through the supervisory relay 35, and the cut-oil relay 18, as described with reference to the answering side of the cord circuit. The operation of the cut-oil'I relay would open the circuit of the line signal 19 at the normallyclosed contacts 20 of said relay and remove the ground from the sleeve side of the telephone line at its normally-closed contacts 17 preventing the operation of the line relay 1.2. '1`he operation of the supervisory relay 35 closes the circuit of the supervisory lamp 34 at the normally-open contacts of said relay and severs the connection'between the tip strand of the cord circuit and the tertiary winding of the operators induction coil at its normally-closed contacts, unit-ing vthe normally-severed parts of said strand for conversation. Due to the fact that the called subscribers telephone was upon its hook no flow of 'current would result through the supervisory relay 36 and the supervisory lamp 34 would be lighted to indicate this fact to the operator. The. operator would then throw her ringing/key 44 to signal the subscriber, the path for ringing current being -from the generator 43 over the sleeve contacts 'of the plug and jack, line conductor 4, substation ringing ap aratus, line conductor 3, ti strand of the p ug and jack, and back to t e generator through the grounded contact of the ringing key. Upon the response of the called subscriber supe'rvisoryrelay 36 would be energized to extinguish the lamp 34 over a path including conductors 14 and 15, winding 10 of the line relay, line conductors 3 and 4 including the substation apparatus, the sleeve strand of the cord circuit and the winding ofthe supervisory relay 36 to battery. The subscribers would then be in communication, the talking currents being propagated from one line'v to the other through the .interposed condensers 25 and 27 in the strands of the cord circuit. Either subscriber placing his'receiver upon the hook at the termination of the conversation would denergiz'e the corresponding supervisory relay32 .or 36, permitting the armatures of said re ays to drop back and light the associated supervisory signal to inform the"`operator that the conversation had terminated. U on withdrawing the plugs from the jacks 'al parts of the system would be restored to normal condition.

- lWhat I claim as new and desire to secure by Letters Patent is:.

1. In a telephone system, the combination with atelephone line, of a cord circuit for I making connection therewith for conversacircuit jointly control-led by the contacts of f said supervisory relays, substantially as described. l

2v. In a telephone system, the combination with a telephoneline, oi a cord circuit for making connection therewith for conversa- `tion, a third conduct-cr at the central oiiice isolated from the talking circuit,` a cutott` relay and a supervisory relay in said third conductor, a line relay permanently con nected with the line, a source of current, a'

` second supervisory relay connected between said source and the sleeve strand of the cord circuit, a'nd a supervisory signal having its circuit normally open at the contacts of said supervisory relay associated with said third conductor and normally closed at the con tacts of said last mentioned supervisory relay, substantially as described. l

3. `In a telephone system, the combination with a telephone line, oi a cord circuit for making connect-ion therewith for conversation, a third conductor at the central otlice isolated trom the talking circuit, a cut-eti relay and a supervisory relay insaid third conductor, aline .relay having two windings, one permanently connected with each line conductor, and a line signal having its circuit completed through the contacts'o'f said line and cut-oit rel ys, a source oi' current, a second supervisory relayconnected between said source and the sleeve .strand of the cord circuit, and a supervisory signal having its circuit normally open at the contacts of said supervisory relay associated with said third conductor, said relay being in a circuit local to the central oilice, and normally closed at the contacts of said? last mentioned relay, said relay being in the path of current to the substation, substantially as described.

4. In a' telephone system, the combination with a telephone line, of a cord circuit for" p. making connect-ion therewith for conversation, a third conductor at the centralotlice isolated Vfrom the talking circuit, a cut-oit` relay and a supervisory relay i-nsaid third conductor, a line relay having two windings, one permanently connected with each line conductor, aline signal having its circuit completed through the contacts'of both said rela'-'s, a source of current, a second supere visory relay connected between said source and the sleeve strand of the cord circuit, said second supervisory relay being substituted in the line for one of the windings oi said line relay when a` connection is established for conversation, and a supervisory signal having its circuit normally open at the contacts oi said supervisory relay associated with said third conductor, vand normally closed at the contacts of said last-mentioned supervisory relay, substantially asdescribed.

5. In a telephone system, the combination with a telephone line, oia cord circuit for connecting therewithfa third conductor at the central otlice, .a cut-oli relay anda supervisory relay in. said third conductor, a line relay permanently connected with the line, a source of current, a second supervisory relay 'connected between said source and a strand ot the cord circuit, and a supervisory circuit jointly controlled by the contacts of said supervisory relays, substantially as described.

'7 In-a telephone system, the combination ywith-a telephone line, oi' a cordy circuit connected therewith, a third conductor isolated from the talking circuit, a cut-0R relay and a supervisory relay in said third conductor, a source of current, a line. relay with its -windingV permanently connected between a limb ot' the line and a pole of said source, a second supervisory relay connected between the ot er pole oi' said source and a strand of the cordcircuit, and a supervisory signal having itscircuit jointly controlled by the contacts of said supervisory relays, substantially as described. f

8. In a telephone system, the combination fwith a telephone line, of a cord circuitconnected therewith, 4a third conductor isolated frornt-he cord circuit, a supervisory relay in aid third conductor, a source oi current, a

second supervisory relay connected between isc the other pole of said source and the strand and State of illinois, in the presence of two of said cord circuit connecting with the other witnesses.

limb of the telephone line', and a supervisory T signal having its circuit jointly controlled by CHARLES S' NI-ASTON' 5 the contacts of seid supervisory relays, sub- 'Witnessesny stantiall as described. f C. B. CAMP,-

Signetl7 by me at Chicago, county of Cook, (1x0. BRADBURY-

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