Patent GB-175611-A (GB)
Abstract: 175,611. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Ray, A. J., and McElyea, H. B.). Feb. 19, 1921, [Convention date]. Automatic exchange systems.-A connection between subscribers A, Fig. 2. and A<1>, Fig. 6, in two subordinate or community exchanges (C.A.X.s) is established and supervised by an operator at a main exchange over a single trunk 131, 132, Fig. 1. This trunk terminates at one of the subordinate exchanges in a pair of linked selectors D<1>, D<2>, Fig. 3, the connection to one subscriber (through the selector D<1>) being established and supervised over the trunk wire 131, and the connection to the other subscriber (through the selector D<2>) over the trunk wire 132. Each C.A.X. is equipped with group selectors and connectors and the subscribers can set up their own local connections, but the assistance of the main-exchange operator is needed in obtaining any external connection. The nearer C.A.X., shown in Figs. 2, 3, and 4, is connected to the main exchange by several trunks, such as 131, 132. The more distant C.A.X., shown in Figs. 5 and 6, is connected bv a single trunk 394, 395 to the near C.A.X. but has no direct trunk connections to the main exchange. The trunk 394, 395 terminates at each end in selector-repeaters G, G<1>, which for outgoing calls act merely as repeaters and for incoming calls act as selectors in response to the first digit received and as repeaters for subsequent digits. The trunk 394, 395 passes through a wayside station Q, Fig. 4, and is wired to terminals in the second and third levels of the selector D<2>. To extend a connection to the distant C.A.X. over the trunk 394. 395, the operator calls the digit 2. If she calls the digit 3 she obtains access to the same trunk over a different route, including the relay set P, and the effect of any subsequent digits is to energize a relay of the set P to throw ringing current on the trunk to ring the subscriber Q. If a subscriber wants an external connection he calls the operator (A and Q by the digit O, A<1> by the digits OO) and then disconnects himself, and the operator sets up linked connections to the calling and wanted subscribers. One of the features of the invention corsists in a set of relays E, Fig. 1, for throwing ringing current momentarily on to the trunk 131, 132 to operate a calling signal 143 at the operator's position. Calling the main-exchange operator by a subscriber A, Fig. 2, at the near C.A.X. The subscriber's line switch C connects him to a selector D which he operates to its tenth level to engage a circuit such as 106, 107, 108 leading to an idle main exchange trunk 131, 132, Fig. 1, whereupon relays 120, 122 of a relay set E become energized, followed by relays 121, 123. The relay 121 causes the successive de-energization of the relays 122, 123, but for a short interval ringing current is connected by the relay 123 to the trunk line to energize the drop signal 143 at the main exchange. The operator plugs into the jack J, taken the numbers of the calling and wanted subscribers, and instructs the calling subscriber to disconnect himself. When he does so the relays 120, 121 relapse. The relay 121 removes ground from the circuit 109, 107 to release the calling connection and completes a circuit 131, 163 to energize a relay 139 in series with the relay 204 of the repeater F, Fig. 3. The relay 139 lights a lamp 147 in front of the operator. The relay 204 bridges the trunk 225, 226 to prepare the selector D<1> for operation and energizes a relay 200, which grounds the wire 107 to mark the main-exchange trunk non-selectable. Recalling of the subscriber A, Fig. 2, by the operator. The operator throws a key K upwards to connect her dial S<1> instead of the relay 139 in the circuit 163 of the relay 204, Fig. 3, and operates the dial to control the selector D<1> and a connector H, Fig. 2, which operate in known manner in response to the impulses repeated by the relay 204 in the trunk 225, 226. If the line A is busy the operator hears a tone signal and releases the comection by means of a key K<1>, but otherwise it is rung by the connector H in the usual manner. The reversal of the current in the trunk 225, 226, Fig. 3, when the subscriber A answers, energizes the electropolarized relay 202, which energizes the relay 203, which locks the relay 200, locks the bridge across the trunk 225, 226, and transfers the control circuit 163 from the ground-connected relay 204 to the batteryconnected relay 205, so that if the operator has meanwhile restored the key K, the relay 139 is de-energized and extinguishes the supervisory lamp 147. Connection by the operator to a subscriber A<1>, Fig. 6, at the distant C.A.X. The operator inserts the other plug of the cord in the jack J<1> and throws the key K downwards to connect her dial S<1> to the control circuit 164 terminating in the relay 275 of the repeater F<1>. Fig. 3, which energizes the relay 276 and bridges the trunk 283. 284. The digit 2 signifying the distant C.A.X. is repeated by the relay 275 to the trunk 283, 284 to operate the selector D<2> to its second level to test and seize (if idle) the circuit 252, 254 associated through the circuits 368, 369 and 386, 387 with the trunk 394, 395. The switching relay 287 connects ground over the jumper 300, wire 256, and contacts 381, 346, 303, 362, 353 to relay 330. At the same time the line relay 331 is energized and energizes a relay 335, which grounds the holding wire 256 by way of contacts 366, 303, 346, 381. The relay 331 also energizes the relay 329 in series with the relay 407, Fig. 5, in a simplex circuit which extends over the two sides of the trunk 394, 395 in parallel. The relay 329 opens the circuit of relay 330, which is sluggish and has not yet become energized. The relay 407 energizes the relav 402 which marks the selector-repeater G<1> non-selectable to local selectors. The second digit is repeated by the relay 331 over the simplex circuit to the relay 407, which repeats it to the relay 401 and vertical magnet 412, and the switch G<1> then rotates in known manner to find an idle connector H<1>. Fig. 6, whereupon the switching relay 403 becomes energized and bridges the connector trunk through the lower winding of an electropolarized relay 408. The two final digits are repeated by the relay 40'i at contact 432 to operate the connector H<1> in the usual manner to select and ring the line A<1>. Speaking circuit; supervision and release. When the subscriber A<1> answers, the reversal of current in the trunk 473, 475 energizes the electropolarized relay 408, Fig. 5, which transfers the simplex control circuit from the ground-connected relay 407 to the battery-connected relay 404, at the same time locking the relay 407. The relay 329, Fig. 4, at the other end of the simplex circuit is thus de-energized and energizes the relay 330, which reverses the current in the trunk 252, 254 to energize the electropolarized bridge relay 278, Fig. 3, which energizes the relay 279, which transfers the control circuit 164 from the groundconnected relav 275 to the battery-connected relay 280, so that, if the operator has meanwhile restored the key K, the relay 140 is de-energized and extinguishes the lamp 148. The two subscribers can now converse, since the connections that have been established to them both originate in the trunk 283, 284, Fig. 1, and the operator can also listen in if she desires. When the subscriber A' disconnects himself operations occur which result in the lighting of the lamp 148. In the same way when the subscriber A disconnects himself the lamp 147 is lit. The operator releases the connection by withdrawing her plugs. For example, when the plug is taken out of the jack J<1> the control circuit 164 is connected to ground so as to de-energize the relays 275, 276, Fig. 3, opening the bridge across the trunk 283, 284 so as to release the selector D<2> and selectorrepeater G, Fig. 4, and the relapse of the relay 335 transfers the simplex circuit to the groundconnected relay 332 so as to de-energize the relays 407, 402, Fig. 5, whereby the magnet 415 is energized to release the selector-repeater G<1>. If a subscriber, say A<1>, fails to disconnect himself, the operator can still release the connection. The removal of the plug from the jack J<1> grounds the control circuit 164, which in this case is connected to the relay 280, which becomes energized and de-energizes the relays 276. 278. 279, so that the bridge across the trunk 283, 284 is opened and the selector D<2> released. The consequent deenergization of relay 335, Fig. 4, connects ground to the simplex circuit, which in this case is connected to relay 404, which becomes energized and opens the circuit of relay 402, which energizes the release magnet 415. Calls originated by a subscriber A<1> at the distant C.A.X. The subscriber A<1> gets connection with the main-exchange operator by calling the digit O twice. The first digit operates the selector D<3>, Fig. 5, to its tenth level to test and seize (if idle) the trunk 394, 395 to the near C.A.X. The second digit is repeated over the simplex trunk circuit to operate the selector-repeater G, Fig. 4, to its tenth level to seize an idle trunk to the main exchange, for example the trunk 131, 132 may be seized over the wires 106, 107, 108. The further operations are as before described. Calls to the local-battery wayside station Q, Fig. 4. The operator calls this station by the single digit 3, the calling plug being inserted in the jack J<2> and the key K<2> being thrown. The trunk 386, 387 is, as already described, accessible from the second level of the selectors D<1>, D<2>, Fig. 3, through the wires 252. 254, and 368, 389, this being the route employed when extending a call over the trunk 394, 395 to the distant C.A.X., but it is also accessible from the third level of the selector D<2> through the wires 255, 257 and