US1551031A

US1551031A - Telephone-exchange system

Info

Publication number: US1551031A
Application number: US484880A
Authority: US
Inventors: Eugene C Helwig
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1921-07-15
Filing date: 1921-07-15
Publication date: 1925-08-25
Anticipated expiration: 1942-08-25

Description

m Mmmm Aug. 25, 194251t l E. c. HELwlG TELEPHONE EXCHANGE SYSTEM Filed July l5,l 192; n 2 Sheets-Shed 1 E. c. HELWIG TELEPHONE EXCHANGE SYSTEM Filed July 1,5, 192`1 442 shqet-sheet 2 w@ www PQ7 u NWN uw RN QN ENEE N .lil Q PATENT OFFlCE.

EUGENE C. HELWIG, OF HACKENSACK, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application :filed July 15, 1921.

To all tcl/wm t may conce/Mt:

Be it known that I, EUGENE C. l-lnLwie, a citizen of the United States, residing at Hackensack, in the county of Bergen, State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to cord circuits therefor of the so-called universal type; that is, cord circuits which automatically adapt themselves to the character of the lines upon the mere insertion of the plugs into the spring jacks of such lines.

The object of this invention is to provide a cord circuit for use at positions where in addition to handling common battery and local battery manual lines, the operators control automatic switches to select common battery automatic lines using the same cords as are used for the common battery manual and local battery manual or magneto lines.

In accordance with the invention, the cords are provided with a pair of battery feeding bridges containing supervisory relays controlling supervisory lamps and also with a pair of bridges containing relays adapted to be operated by the magnetos of the magneto stations to control the same lamps. A dial is also provided and is automatically associated with the cord taken for use. This dial controls the automatic switches to extend connection to the common battery automatic lines. Current for talking purposes is fed to such lines, when called, from the connector in the well known manner. The response of the called party causes the connector to reverse the current flow in the cord to operate the polarized relay to control the calling supervisory lamp. The operation of this polarized relay also causes a reversal in the current flow in the calling line to operate the meter thereof, so that in the case of a call to an automatic line, the operator is relieved of the work of registering the call.

Referring to the drawings, Figs. 1 and 2 taken together illustrate a circuit arrange'- ment embodying the invention.

A designates a common battery substation, B a magneto substation, and C an automatic substation. The subscriber at substation A, initiates a call by merely removing1 his receiver which causes the operation of Serial No. 484,880.

the line relay 101 to light the lamp 102 before the operator. The subscriber at substation B must actuate his call generator 103 to secure the attention of the operator by actuating the annunciator or drop 154. The subscriber at substation C must actuate his calling dial 105 to set selector brushes 106 upon a level of trunks 107, terminating in jacks 169 before the operator. The selection of one of these trunks causes the lamp 108 to light.

Vith this preliminary description, it is believed the invention will be most readily understood from a description of the operation, and considering first a call from the common battery substation A to the similar substation D, Fig. 2, the operator in response to the lighting of the lamp 102 inserts the plug 109 of the cord into the jack 110, which causes cut-off relay 111 to op erate to deenergize the line relay 101, which in releasing extinguishes the lamp 102 in the well known manner. rIhe circuit for the cut-off relay 111 includes a marginal relay 112 and a relay 113. The relay 112 operates only when the plug is inserted into the jacks 110 and 169 of the common battery lines, but the relay 113 operates when the plug is inserted into jacks associated with either' common battery or magneto lines. Relay 113 in attracting its upper armature disconnects the busy test conductor 113 leading to the operators telephone set, and completes the continuity of the tip conductor of the cord. At its lower armature, relay 113 prepares a circuit for the answering supervisory lamp 1141, which lamp is not, however, lighted at this time due to its being shunted by a circuit that will be described. Relay 112 in operating closes the following circuit for feeding talking current to the calling substation: free pole of bat-- tery, relay 115, inner left armature and front contact of relay 112, lower windin of impedance coil 116, normal contact 117 of relay 118, conductor 119, lower left winding of repeating coil 120, lower talking conductor of the cord, normal contact 121 of relay 122, ring of the plug 109, ring of the jack 110, through the substation equipment returning over the-tip conductor, tip of the jack, tip of the plug, upper talking con ductor of the cord including alternate contact 123 of relay 113, and normal contact 124 of relay 122, upper left winding of repeating coil 120, conductor 125, normal contact 126 of relay 118, conductor 127, upper winding or the impedance coil 116, inner right armature and alternate contact of relay 112 to ground. The operator upon inserting the plug, also actuates her listening hey 200 to connect her telephone set (not shown) across the cord. The answering` supervisory lamp 114 is now shunted over the following path: free pole of battery, outer left arinature and alternate Contact or relay 123 which operates due to the operation of relay 112, conductor 129, resistance 130, conductor 131, inner right armature and alternate contact of relay 12S, arn'iature and alternate contact of relay 115, conductors 132, 201n alternate Contact 202 or' the listening liey 200,

conductors

203, 133, relay 1341 to ground. Relay 131- in attracting its right armature locks itself over the following path ground, relay 1311, its right armature and alternate contact, conductor 135, inner left arinatnre and contact et relay 123, conductor 136, arniature and alternate contact of relay 115, inner right armature and alternate contact of relay 128, conductor 131, resistance 130, conductor 129 through left armature and alternate contact or relay 123 to battery. This locking circuit is independent of the. operators listening key 200, and consequently reinains closed after the listening ley is restored. The operator now secures from the calling subscriber the nuinber of the wanted line, and assuming that the calling subscriber desires to talk with the subscriber at station l), inserts the calling plug 204; in the jack 205 or said line, operating the cutoll relay 206 and marginal relay 20'?v and relay 203. Relay 207 operates only when the plug 201 is inserted in the jacks oli connnor` battery lines ancL does not operate when the plug is inserted into the jacks 209 of inagneto lines, or acls 210 o'l' autoinatic connnon batteryv lines. Relay 20T closes the following circuit for feeding talking current to the substation D: ground, inner left armature and alternate contact or relay 20,7,

conductors

211, 137, upper winding of the iinpedance coil 133, upper right winding cit the repeating coil 120, tip conductor of the cord, norinal contact 212 o1? the ringing key 213, norinal contact 21-1. oit relay 215, alternate contact 210 of relay 211- which relay ope ated when relay 203 operated and opened the test conductor 210, tip of the jack, through the subst n apparatus, ring or' the jack, ring ol the pl norinal contact 220 of relay 21:3, norinal c act 221 of the ringing liey 213, lower tall ng conductor ot the cord, lower right winding oit the repeating coil 120, lower winding et the impedance coil 138,

conductors

139, 222, inner right armature and alternate contact of relay 20T, relay 223, conductor 239, contact 224 to tree pole to battery. The operator now actuates her ringing key 213, impressing ringing current 'troni generator 225 on the called line. `Upon the response o1 the called party, talle ing current is led over the path traced to the called substation.

Upon the replacing or' the receiver by the calling party, the answering supervisory lanip 11,41 is lighted over the following circuit: ilree pole or battery, outer le 't urinature and alternate contact or relay 123, conductor 12), resistance 130, lainp 114, conductor 1112, lower arinature and contact o1" relay 113 to ground. The shunt about larnp 1111 was opened due to the release ol' relay 115 when the calling party replaced his receiver. The replacing of the receiver by the called party lights the called supervisory `ainp over the following circuit: 'lrce pole ot battery, outer right arniature ci" relay 207, arniature and norinal contact ot relay 223, conductor 270, resistance larnp 2G, lower arniature and contact oi relay 1T to ground. The operator with4 draws the plugs from the jacks, the withdrawal ot the plug 109 restoring the apparatus to norn'ial.

@mamon balli/'cry mai-malto local Ziatzfcry/ magneto.

1n a call et this character the operations are the saine as those described up to the point where the operator inserts the plug into the iat-1v .209 ot niagneto line E. This operates the cut-oli" relay 223 ol the niagneto line and relay 203. ll/larginal relay 20.7 reinains inert due to the resistance of the cut-oli" relay 22S. Relay 20S, as before, operates relay 21T to cut oil' the busy test conductor 210 and complete the continuity et the tip conductor of the cord. Relay 20iremaining inert leaves the polarized relay 220 briaged across the cord circuit. The operator, by nieans of ringing liey 213 new signals the subscriber at substation lE. The transmitter of substation 1G energized by the local battery 230, and the relayr 207 in remaining inert inaintains the connnon battery feed disconnected troni the cord.

lllhen the sul scriber at substation E actuates generator 231 to indicate to the operator that the conversation is concluded, the polarized relay 229 operates over the tip and ring conductors of the cord in series, lightingv the lan'ip 226 over the following circuit: 'tree pole of battery, norinal contact f el" relay 235, conductor 239, relay 223, inner right armature and normal Contact or relay 20.7, conductor 2110, norinal contact el relayv 235, cnnductor 233, alternate contact ci relay 220. conductor 232, resistance 22T, lainp 220 to ground on the lower armature and alternate Contact et relay 217. lle ay 223 in operating` closes a locking circuit for the lainp 226, maintaining the saine ri `rn l fri,

lttllllwllllllll lighted after the subscriber E ceases to turn his generator. This circuit is as follows: free pole of battery, contact 224, conductor 239, relay 223, inner right armature and normal contact of relay7 207, conductors 240, 236, normal contact 237 of the listening key, conductor 238, armature and alternate Contact of relay 223, conductor 270, resistance 227, lamp 226 to ground at the lower armature and alternate contact of relay 217. ln response to the lighting of the. lamp 226, the operator throws her listening key and challenges the called party and if no response is received, withdraws the plugl 204 from the jack 209, which restores the apparatusto normal condition.

Common battery mom-ucl to common buttery automatic.

A call of this character requires the same operations as that traced up to the point Where the operator inserts the plug 204 into the jack 210, this j ack terminating in an incoming selector at the automatic exchange the brushes 241 only thereof are shown. As in the case of the magneto call, marginal relay 207 remains inert, and

relays

208 and 242 operate. Relay 208, as before, operates relay 217. Relay 207 in remaining inert maintains the polarized relay 229 across the cord and holds open the-battery feeding bridge. Talking current for the called substation F will be fed from the connector in the well known manner over the windings of relay 243.

The operator now turns the dial 244 for the first digit of the want-ed number to set the selector 241 to the desired level, whereupon it automatically picks out a second selector, the brushes 245 only whereof are shown, which selector will be set by the dial. As the dial moves olf normal for the first digit it closes contact 246 to operate relay 247. Relay 247 closes the following circuit for operating relay 215: free pole of battery, relay 215, conductor 248, inner left armature of relay 235, conductors 249, 143, outer right armature and back Contact of relay 144,

conductors

145, 250, alternate contact 251 of key 200, conductor 252, inner right armature and alternate contact of relay 247, conductor 258 to ground at the armature and normal contact of relay 253. Relay 215 locks itself over the following circuit: free pole of battery, relay 215, its alternate Contact 254, conductor 255, normal contact of polarized relay 256, outer righthand contact of relay 257, relay 253 to ground. Relay 253 in attracting its armature removes ground from the conductor 258, thus preventing the dial from being associated with another cord circuit as long' as relay 253 is operated. Relay 215 in attracting its armature 259 operates relay 235, which in attracting its inner right armature locks itself to ground at the lower armature and contact of relay 217. The impulse relay of the incoming selector 241 operates as soon as the operator inserts the plug into the jack to prepare the circuit of this selector. This circuit includes the tip of the jack 210, tip of the plug 204, contacts 216, contacts 214, 212, upper righthand winding of repeating coil 120, upper winding of impedance coil 138,

conductors

137, 211, outer left armature and back contact of relay 207, relay 229, conductor 222, conductor 139, lower winding of impedance coil 138, lower right winding of repeating coil 120, lower talking conductor, contacts 221, 220, lower talking conductor to the ring of the plug.

As soon as the dial is moved off normal, and relay 215 .is operated, the impulse contact 260 is substituted for the bridge just traced. This circuit may be traced from the upper talking conductor, upper contact 261 of relay 215, conductor 265, outer left armature and alternate contact of relay 247 impulse contact 260, conductor 263, alternate contact 264 of relay 215, to the lower talking conductor. The dial in returning to normal position interrupts this bridge to set the incoming selector 241, whereupon it automatically hunts for and seizes a second selector 245. l/Tfhen the dial reaches its normal position and releases relay 247, a bridge including polarized relay 256 is substituted for the bridge including only the impulse contact 260. This circuit may be traced from contact 261,

conductors

265, 266, relay 256, conductor 267, impulse contact 260, conductor 263, contact 264, this bridge preventing premature release. The operator now turns the dial for the next digit to set the selector 245 to the level leading to connectors serving' the group of lines containing substation F, whereupon this selector hunts for and seizes one of these connectors. As the dial is moved off normal, the relay 247 again operates to shunt out the relay 256 and leaves only impulse contact 260 across the loop leading to the automatic office. The operations involved in setting the connector for the tens and units digits will not be described in detail since they are the same as those involved in setting the incoming selector and second selector. The connector tests the called line in the well known manner, and if found idle, applies ringing current thereto to signal the called party.

Upon the removal of the receiver by the called party, relay 243 reverses the direction of current flow, thus operating polarized relay 256, which opens the locking circuit of relays 215 and 253. Relay 215 disconnects the dial and associated relays from the cord, and completes the talking circuit, and relay 253 in restoring renders the dial accesand bach` contact olE relay 217, condenser 275 conductor 270, to the head set. The opera-toi tl intorms the calling party that the line busy or operaties key 209 to release relay 215, allowing` this busy tone to be ti if fnit -u to the calling line through the 'ci coil 120. Upon tl e replacei receiver by the calling` party aufl liohtina; ot the lamp 11., the operator thdrays the plugs :trom the aclzs Y 1 r. a res the apparatus, including the au- `emr-tic switches, to normal position. ln lase the call is successful, the replacement the receiver by the subscriber at substation l? again reverses the direction ot current tloiv in the cord, .vhicli causes the lamp 220 to light over the following` circuit: tree pole ot battery,l outer lett armature and alternate Contact ot relay 235, nornuii contact ot rel y 229.

conductors

232, 270, resistance i lamp to 1Qfround at the lower armature and contact olf relay 217. 1i the operator actrates lrey 269 atter she has turned 'the dial for the last time, but lie'lore the dial has reached its normal position. this does not unlock relay 215 and 253, due to a circuit being' closed for these reaiys at the outer right armature and alternate contact ot relay 217, which ren'iains operated until the dial reaches its normal position. Relay 211i' releases each time the dial reaches normal position and at its outer lett armature connects the tone conductor 2?0 to the ring` conductor of the cord so that tones on such conductor, if present, are transmitted to the operator between operations oit the dial, as for example, it the incoming' selector 2-11 or second selector 24:5 encounters a busy trunk group.

V1`he response ot the called party F in operatino` the polarized relay 229, actuates relay 113 (lP 1) to reverse the direction ot current vlion' in the calling` line to operate the meter 1-10 thereo'l, assuming thatl the calling` station is a common battery automatic substation which is provided With a meter. This meter may be ot the type shown in Patent No. 1,170,269 ot' `March 21, 1910 to A. l1, Blessing. The circuit for operatingrelay 113 is as follows: free pole oi? battery, relay 113,

conductors

147, 271, alternate Contact 272 ot relay 235, conductor 233, alternate contact ot' relay 229,

conductors

232, 270, resistance 227, lamp 226 to Maf/acto Zinc to common, battery Zinc.

ln a call ot this character the marginal relay 112 does not operate when the plug- 109 is inserted in the jack 151, and maintains the battery feed disconnected from he calling;l line, leaving' a relay 152 adapted to be operated by alterna-tin` current bridged across the cord. The relay 113, however, operates in series with the cut-olii' relay 153, the former relay disconnecting the busy test conductor 113 and completing` the continunity olf the tip conductor ot the cord, and the latter relay cutting oli' the drop 15st; ot the magneto line. The operator throws her listening key 200 and inquires the number ot the desired line, and extends the connection to line D, Fi or F as already described.

Upon the termination of the conversation, the subscriber at substation ll operates his generator 103, Which energizes relay 152. Relay 152 closes a circuit to operate relay 115 follows: tree pole ot' battery, relay 115, inner left armature and back contact ot relay 112, armature and alternate contact 01':x relay 152, outer left armature and normal contact of relay 128, conductor 129, resistance 130, lamp 1141, conductor 142, to ground at the lower armature and alternate contact ot relay 113. Relay 115 in operatinT locks itselt over the following circuit to maintain the lamp 114 lighted after the party at substation B ceases to turn generator 103: tree pole ot battery, relay 115, inner le'lt armature and back contact ot relay 112,

conductors

155, 273, normal Contact 2-/1 of key 200, conductors 201, 132, 136, armature and alternate Contact of relay 115, conductor 150, outer lett armature and normal contact ot relay 128, conductor 129, resistance 130, lamp 114, conductor 1412, to ground at the lower armature and alternate contact ot' relay 113. The operator in response to the lighting of' lamp 114 actuates listening key 200, which extinguishes the lamp, and challenges the calling` party, and it no response is received, removes the plugs 109 and 2011L from their jacks, which restores the apparatus to normal condition.

The cord circuit is provided With a pair of lreys RK, CK for impressing positive or negative high potential current on the substations provided With coin boxes 159. These coin boxes may be ot the type shown in Patent No. 1,043,219, Nov. 5, 1912 to O. F. Forsberg. It the coins are t0 be colllO lected, the operator actuates collect key CK. The closure of contact 160 opeates relay 122, and the closure of contact 161 applies high potential positive current to the tip and ring ci the cord by way oi the armatures of relay 122 to ground through the polarized magnet of the coin botes 159 in the well known manner, this i'nagnet operating to collect the coins. The closure o1` Contact 163 ot the key operates relay 118 which at its armature 148 locks up to the lower armature and alternate contact of relay 113, and in attracting its armature 164 prepares a circuit tor lighting the coin pilot lamp 165, this circuit being closed by a relay 162 which operates in series with the coin collect current it the coins have been deposited. lf no coins were deposited, no ground would be present at the substation as described in said Forsbergl patent, and this relay would remain inert and lamp 165 would not light, thus notifying the operator that no coins were deposited. lt the substation such as C is provided with a meter 146 instead of a coin box, as in station A, and the called line is either a line such as D or E, and the call is successful, the operation oll the collect key CK operates the relay 118, as described, which reverses the current flow in the calling line to operate the meter of such line in the well known manner. lf the coin or coins are to be refunded, the operator actuates refund key RK, which operates relay 122 over contact 166, and the closure of contact 167 impresses high potential negative current on the tip and ring of the line by way ot the armatures and iront contacts ot relay 122 to the polarized magnet in the coin box 159, which magnet refunds the coins to the subscriber. The coin pilot lamp 165 operates due to the operation of relay 168 in the coin current circuit. Lamp 170 is the register pilot lamp and is operated when the reversing relay 118 operates to operate the calling line meter. 1t supervises the operation of this reversing relay.

Relays 172, 173, interrupter 174 and bell 175 are provided to furnish a recall signal for lines such as A and C. The calling party desiring to resignal the operator for any reason moves his switchhook up and down. The first interruption ot the line cicuit releases relay 115 which releases relay 134. When 115 again energizes, relay 134 in its retracted position operates relay 172 over a circuit including the retracted armature ot relay 173, right winding of relay 172, resistance 176, lett retracted arma ture of relay 134, outer right attracted armature ot' relay 128, conductors 177, 273, contact 274 or key 200, conductors 201, 132, 136, attracted armature of relay 115, inner right attracted armature of relay 128, conductor 131, resistance 130, outer left attracted armature of relay 128 to battery. Relay 172 in attracting its armature connects the interruptor to its lett winding in series with relay 173 and when a metallic segment reached it holds relay 172 operated through its lett winding and operates relay 17a which opens the shunt about lamp 114. llVlien the next insulated segment is reached relay 173 falls back again closing the shunt to again put out the lamp and operate relay 172 preparing a circuit 'for the next metallic segment. Thus the lamp flashes to attract the attention of the operator. 1in audible signal in the form of a single tap bell 17 5 is also provided which is tapped each time relay 173 operates.

`What is claimed is:

1. In a telephone system, the combination with common battery manual lines terminating in jacks, local battery magneto lines terminating in jacks, common battery automatic lines, and operators position, automatic switches, the first of said switches terminating in a. jack at said position, and a cord circuit having a. dial associated there with for controlling said switches to connect with said automatic lines, said cord circuit having a pair of battery feeding bridges and, a second pair ot bridges containing alter`- nating current relays, said cord circuit including means automatically operated upon the insertion of the plugs of the cord into the jacks for including certain of said bridges in said cord for adapting the cord to the character of the connected lines.

2. ln a telephone system, the combination with common `battery manual lines terminating` in jacks, local battery magneto lines terminating in jacks, common battery automatic lines, an operators position, automatic switches, the `first of said switches terminating in a jack at said position, cord circuit having a dial associated therewith for controlling said switches to connect with said automatic lines, said cord circuit having a pair of battery 'feeding bridges containing supervisory relays, a second pair ot' bridges containing alternating current relays, supervisory lamps controlled thereby, said cord circuit including means automatically operated upon the insertion of the plugs of the cord into the jacks, for including certain oi said bridges in said cord for adapting the cord to the character of the connected lines.

3. In a telephone system, telephone lines, a lcord circuit, automatic switches, a dial for controllingthe same to connect with said lines, a key, a relay for connecting the dial to the cord, a circuit therefor closed when the cord is taken for use, a locking circuit for said relay, acontact therein, a relay adapted to open the same when the key is operated to unlock said relay to disconnect the dial from the cord, a shunt circuit about said contact, and a relay adapted to close the same when the dial is in an off-normal position.

4. In a telephone system, telephone lines, a trunk line terminating,y in an a-utoniatic switch, a cord circuit for interconnecting;- said lines, a dial associated with said cord circuit for controlling said switch, a relay for connecting` the dial with the cord, operated when the dial is moved off normal, a locking' circuit for said relay including' contacts of a second relay` an energrizing` circuit for said second relay controlled by a key. ashunt path around said contacts of the second relay controlled by a third relay, and an energizing,` circuit Jfor said third relay closed while said dial is in an oil-normal position.

5. In a telephone system, telephone lines, a trunks line terminating` in an automatic switch, a cord circuit for interconnecting' said lines, a dial associated with said cord circuit for controlling' said switch, a relay for connecting` the dial with the cord, operated when the dial is moved oft7 normal, a locking` circuit for said relay including contacts of a second relay, an energizing circuit :tor said second relay controlled by a key, whereby said locking' circuit may be broken to disconnect said dial from the cord and means controlled by said dial for maintaining said locking circuit closed independent oi said key.

6- In a telephone system, the combination with common battery manual lines and local battery magneto lines .terminating in acks, common battery automatic lines, an operators position, automatic switches, the lirst of said automatic switches terminating` in a jack at said position, and a. cord circuit having a dia-l adapted to be associated therewith for controlling said switches to connect with said automatic lines, said cord circuit having means including' a pair of marginal relays for automatically adapting the cord to the character of the connected lines upon the insertion of the plugs ot the cord into the jacks.

7. In a telephone system, the combination with common battery manual lines and local battery manual lines terminating in jacks, local battery magneto lines terminating in jacks, common battery automatic lines, an operators position, an automatic switch terminating in a jack at said position, and a oord circuit having a dial associated therewith for controlling` said switch to connect with said automatic lines, said cord circuit having means including a pair of marginal relays and a pair of bridges including alternatingcurrent relays for automatically adapting the cord to the character ot' the connected lines upon the insertion of the plugs olI the cord into the jacks.

8. In a telephone system, in combination, common battery manual lines, local battery magneto lines. common battery automatic lines, a cord circuit, and means in said cord circuit including a marginal relay and a bridge includingr an alternating current relay for automatically adapting the cord to extend a call from any one of said lines to any other of said lines.

9. In a telephone system, in combination, common battery manual lines, local battery magneto lines, common battery automatic lines, a cord circuit, a pair of battery feeding* bridges, and a pair of marginal relays operatively associated with said cord upon the interconnection of certain of said lines and not upon the interconnection of other ot' said lines.

l0. In a telephone system, a cord circuit, common battery manual lines, local battery magneto lines and common battery automatic lines adapted to be interconnected by said cord circuit, a irst relay associated with one end of said cord circuit, a marginal relay in series with said lirst relay and means controlled by said marginal relay for adapting' said cord circuit to operatively connect certain ot said lines associated with said one end of the cord to any of said lines associated with the other end of said cord.

11. In a telephone system, a cord circuit, common battery manual lines, local battery magneto lines and common battery automatic lines adapted to be interconnected by said cord circuit, a polarized relay normally bridged across said cord, a marginal relay associated with said cord for removing said bridge from across said cord upon the connection ofi said cord with certain of said lines.

In witness whereof, I hereunto subscribe my name this 14th day of July, A. D. 1921.

EUGENE C. HELWIG.