Patent GB-176889-A (GB)
Abstract: 176,889. Western Electric Co., Ltd., (Western Electric Co., Inc.). Dec. 15, 1920. Automatic exchange systems.-A repeating coil in the talking circuit has its transmission characteristics automatically varied according to the length &c. of the trunk over which the connection is extended, or is cut out of circuit entirely if the connection is extended to a trunk operator's position. In the system ilustrated the sequence switch 100, Fig. 1, can be moved into three distinct talking positions according to the setting of a register switch 237, Fig. 2. In its 12th position only the outer windings of the secondary of the repeating coil 154 are included in the outgoing talking circuit, through contacts 128, 129, 132, 133. In its 13th position, which it assumes when the outgoing line is a long or loaded trunk, all the windings are brought into circuit, to give a higher transiormation ratio. In its 15th position, when connection is made to an operator, the coil 154 is cut out entirely and a clean metallic circuit is switched through at contacts 116, 117. The switch 100 is set to the appropriate position after the wanted connection has been completed through group selectors SS1, SS2, and a final selector FS3, the movement being controlled by the switch 237, which forms part of the register for the first ligit, in conjunction with the counting relays 0, 0<1>, 1, 1<1>, &c., which receive reverting impulses from contact 126. The talking position of the switch 100 may be under the joint control of the registers of two or more digits. Specification 146,425 is referred to. Establishment of connection. The energization of relay 101 when the selector SS1 is seized moves the switch 100 to its 2nd position, in which the magnet 103 hunts the switch FS to find an idle register-controller, Fig. 2, whereupon relay 102 is energized and moves the switch 100 to its 3rd position, extending the calling line to relay 225, which energizes the slow-release relay 226 and moves switch 200 to its 2nd position. The impulses of successive digits are now repeated by relay 225 through the slow-release series relay 227 to the register magnets 233, 234, &c. to set the registers 236, 238, &c., the relay 227 becoming energized at the commencement of each digit to move the switch 200 to an odd-number position and de-energized at the termination of each digit to move the switch 200 to an even-number position. When registration is complete, switch 200 arrives at its 10th position and drives switch 250 to its 2nd position, completing a fundamental circuit through relays 125, Fig. 1, and 265, Fig. 2. A polarized relay 266 in the same circuit is not energized at this stage. Relay 125 drives switch 100 to its 4th position, energizing the up-drive magnet 104 to raise the selector SS1, and the commutator 145 intermittently short-circuits relay 265 which repeats impulses through the register 236 to the counting relays 2, 2<1>, 1, 1<1>, &c. These operate in known manner so that after a number of impulses corresponding to the setting of register 236 relay 0<1> is energized, driving the switch 250 to its 4th position and opening the fundamental circuit to de-energize relay 125, which stops the selector and moves switch 100 to its 5th position. The fundamental circuit is now again closed, re-energizing relays 125, 265, and switch 100 is moved to its 6th position, again energizing the up-drive magnet 164, Reverting impulses are now produced by commutator 144 to shortcircuit relay 265, which repeats them through register 238 to the counting relavs until relay 0<1> is again energized, driving switch 250 to its 6th position and opening the fundamental circuit to de-energize relay 125, which moves switch 100 to its 7th position. The two movements of the selector that have so far taken place have selected and tripped a particular set of brushes 135, 136, 137 and raised them to the first of a particular group of terminals, and a hunting movement now takes place to find an idle trunk in this group. Relay 125 is energized over contact 118 and moves switch 100 to its 8th position, at the same time locking itself to the test wiper 137 so as to energize the up-drive magnet 104 until an ungrounded terminal 140 is found, whereupon relay 125 relapses and moves switch 100 to its 9th position, grounding the test wiper through contact 126. Relay 125 is energized again over contact 118 and drives switch 100 to its 10th position, the relay remaining locked in a circuit through contact 108. Relays 325, Fig. 3, and 265, Fig. 2, are now energized in a fundamental circuit which extends over both sides of the trunk 138, 139, contacts 129, 128, switch arms 120, 121, and both windings of polarized relay 266. The selector SS2, Fig. 3, is operated in a manner closely similarly to that already described for the selector SS, under control of registers 238, 239, and when a final selector FS3 has been seized the switch 300 moves to its 8th position, extending the fundamental circuit to relav 425 over contacts 303, 331, 364, 363. 362. The final selector operates, under the control of registers not shown in Fig. 2, to select the wanted line, and if this line is idle the switch 350 moves into its 15th position. When the switch 350 moves out of its 8th position, preparatory to testing the selected line, it opens a circuit 359, 329, 302 by which relay 325 is locked, and switch 300 is driven to its 9th position, in which relay 325 is again energized over the fundamental circuit through contacts 333, 304. The direction of the current in the fundamental circuit is now reversed, relay 325 being connected to the lower instead of the upper trunk wire and ground connected to the upper wire through contacts 303, 308, 334, and the polarized relay 266, Fig. 2, becomes energized for the first time. Relay 266 drives switch 250, which was in its 16th position, to position 16 1/2, and also energizes relay 148, Fig. 1, which unlocks relay 125 so as to drive switch 100 to its 11th position- The fundamental circuit including relays 325, 266 is opened at springs 128, 129 and the relapse of these relays drives switches 300, 250 to their 14th and 17th positions. Operation of switch 100 to different talking positions. With the switches 100, 250 in their 11th and 17th positions a fundamental circuit is closed through relay 125, contact 122, switch arm 120, relays 265, 266, and contact 263. Relay 125 drives forward the switch 100 which, at each halfstep, short-circuits relay 265 through contacts 126, 122. These impulses are repeated by relay 265 over wire 284 and register 237 to the counting-relays 2, 2<1>, 1, 1<1>, &c., which build up in the well-known manner until, after a number of impulses determined by the setting of the register 237, relay 0<1> is energized, driving switch 250 to its 18th position and opening the fundamental circuit to de-energize relay 125. The switch 100 is thus moved to either its 12th, 13th, or 14th position. If, however, connection has been made to an operator's position, in which case the switch 100 is moved to its 14th position, the current from the operator's circuit is of the right direction to energize a polarized relay 131 which keeps relay 125 energized until the switch 100 reaches its 15th position. Release of the register controller. When the switch 100 leaves its 11th position it opens the circuit of relay 225, Fig. 2, and on the de-energization of relay 125, which keeps a locking- ground on switch-arm 114, relay 226 also relapses and drives switch 200 to its 15th position closing circuits from an interrupter 295 through off normal contacts ON and magnets 233, 234, &c. for restoring the registers 236, &c. When all the registers are restored a circuit is closed through normal contacts N to drive switch 200 to its 1st position. In the meantime a circuit 241, 261 has been closed to drive switch 250 to its 1st position. Remaining operations. Ringing current is supplied to the wanted line B from the second selector SS2 in the 14th position of switch 300, which moves to its 16th position when the call is answered. When the switch 100 left its 11th position, relay 153 which was previously energized over contact 108 was kept energized by relay 152 in :he calling subscriber's loop. When the calling subscriber disconnects himself, relays 152, 153 relapse and the switch 100 moves to its 18th position, energizing the down-drive magnet 106 to restore the selector SS1, and the complete restoration of the whole connection ensues in known manner. In the case of a connection to an operator's position, relay 152 is cut out of circuit at contact 116 when the switch 100 approaches its 15th position, but at the same time an alternative looking circuit for relay 153 is closed through contact 151. Relay 125, which was kept energized by relay 131 in the 14th position of switch 100, is locked in the 15th position over contact 26 and test brush 137. The operator releases the connection by opening this locking circuit to de-energize relay 125, which moves the switch 100 to its 16th position, in which contact 151 unlocks relay 153.