211,639. Western Electric Co., Ltd., (Western Electric Co., Inc.). Dec. 21, 1922. Automatic exchange systems.- In a system employing registercontrollers, the subscribers at a private branch exchange are designated in the public direct. ory by the same number of digits as those at the main exchange, and connections thereto are established over special connections. In the arangement described, the special connector, Fig. 2, serves two P. B. Xs having 60 and 40 subscribers respectively and hunts in the level corresponding to the tens digits of the wanted number for an idle trunk leading to a connector, Fig. 3, at the required P. B. X., the trunks to each P. B. X. being multipled in the levels over which it is accessible. At the same time, the tens digit is recorded on a register 290 individual to the special connector by the restoration of the trip spindle magnet 248, and the P. B. X. cannector operates under the control of this register and the units register at the register-controller. Means are provided whereby the trunk is released simultaneously at both ends. Special connector, Fig. 2. The calling line is extended to a register-controller 130, 140, 150, Fig. 1, at contacts 103, 104 by control switch 100 at the first group selector, which is subsequently operated under control of the hundreds register 130 to select a special connector leading to the required P. B. X. Relay 243, Fig. 2, energizes over the testwiper 111 in series with relay 107 and locks, and the fundamental circuit is closed over wipers 109, 110, for relays 252, 126. Relay 252 moves sequence switch 250 into the 2nd position in which the trip spindle magnet 248 operates. The interrupter brush 230 engages with spring 231 in all off-normal positions, and causes springs 231, 232 to make contact at each step of the magnet, shunting stepping relay 126 over contact 249. In the 10th position of sequence switch 120, prior to the closure of the fundamental circuit, differential relay 127 is connected over both its windings, one being in series with the tens register 140, which energizes and advances one step, and the left winding of relay 127 is shunted at master contact 141 between positions, so that it energizes over the right winding. When relay 126 energizes in the fundamental circuit, relay 127 is released, and at each shunting of relay 126 an impulse is sent to the register 140, until, in normal position thereof, sequence switch 120 is moved to the 12th position and relay 125 energizes and breaks the fundamental circuit, whereupon the magnet 248 comes to rest and sequence switch 250 moves to the 3rd position, in which relays 263, 262 energize and connect up magnet 261 to trip the selected wipers. In off-normal position relays 262, 263 are released in turn at brush 235, opening the circuit of magnet 261 and energizing relay 252, which again connects up magnet 248, which rotates to normal. At each step an impulse is sent to the individual register 290 over the left winding of differential relay 259 and contact 257, relay 259 being intermittently energized over its right winding at master contact 291, so that register 290 receives the same setting as the tens register 140. Relay 252 falls back and connects up magnet 261 to initiate hunting for an idle trunk in the selected level. When this is found, test relay 264 is energized by battery over the test terminal and cut off relay 287, and marks the trunk busy by completing a parallel low resistance circuit over relay 262, which energizes, opening the driving circuit and moving sequence switch 250 to the 5th position. P. B. X. connector, Fig. 3. Relay 373 is energized by alternating current over the trunk in series with a resistance 375 and condenser 303 and an inoperative marginal relay 260, locks and connects up relay 360 which advances sequence switch 350 to the 2nd position, in which the test wire 305 is opened to mark the trunk busy to local switches. Resistance 375 and condenser 303 are shunted, and relay 260 energizes, advancing sequence switch 250 to the 6th position, in which relay 252 energizes over contacts 249, 274. Alternating current is disconnected from the trunk, and relays 373, 360 fall back, advancing sequence switch 350 to the 3rd position, in which relay 372 energizes and completes a circuit over the trunks for relays 352, 279, whereupon relay 252 releases and moves sequence switch 250 to the 7th position. The fundamental circuit is closed, and relay 252 drives sequence switch 250 to the 8th position, relay 272 being momentarily energized at master contact 238 to release relays 279, 352, so that relay 259 energizes over its right winding and isolates the register 290. Release of relay 352 advances sequence switch 350 to the 4th position. Relays 279, 352 again energize, releasing relay 259 and connecting up the trip spindle magnet 348. At each step, relay 279 is shunted over contact 349 and springs 355, 357, operating the register 290 in series with the left winding and in parallel with the right winding of relay 259, which energizes between positions by the shunting of its left winding at master contact 291. When the register 290 is restored to normal, relay 272 operates in parallel with sequence switch 250, releasing relay 352 when springs 355, 357 are opened, and sequence switch 350 advances to to the 6th position. Sequence switch 250 moves to the 10th position in which relay 272 energizes and connects up relays 279, 352, operating the magnet 361 to advance the selected wipers. At each step, relay 279 is shunted at interrupter brush 306, and upon release, shunts relay 126 in the fundamental circuit over contacts 249, 274 and operates the units register 150. In normal position, relay 125 energizes in series with sequence switch 120 and opens the fundamental circuit. Relay 252 releases and drives sequence switch 250 to the 12th position, while relay 272 energizes and open-circuits relay 352, advancing sequence switch 350. Relay 272 falls back and connects up relays 279, 352. Busy test; supply of ringing current. If the wanted line is idle, relay 364 is energized in the 7th position by battery potential on the test terminal, and connects up its low resistance right winding to mark the line busy. Between the 8th and 10th positions relays 352, 279 are released momentarily to energize relay 252 and move sequence switch 250 to the 13th position. Ringing current is supplied from a source 320 in the 12th position of sequence switch 350, and upon reply of the called subscriber, cut-off relay 360 energizes and advances sequence switch 350 to the 14th position. Relays 352, 279 fall back. energizing relay 252 and moving sequence switch 250 to the 14th or talking position. Release. The group selector is restored in the usual manner, and relay 243 is released at the test wiper 111, and advances sequence switch 250 to the 17th position, in which relay 252 energizes. Opening of the line circuit releases relay 368, whereupon relay 360 and sequence switch 350 operate in turn to move the latter to the 17th position, in which magnet 361 rotates to normal. Relay 352 energizes over brush 323, opening the driving circuit and advancing sequence switch 350 to the 18th position, in which relays 323, 279 are energized, driving sequence switch 350 to the 1st position and releasing relay 252 to drive sequence switch 250 to the 18th position. The trunk is thus released simultaneously at both ends at contacts 277, 341. Magnet 261 rotates to normal, and is stopped by the energization of relay 262, which advances sequence switch 250 to the 1st position. Busy signal and release. Relay 364 does not energize in the 7th position, but relay 360 energizes and stops sequence switch 350 in the 8th position. Sequence switch 250 remains in the 12th position, and a busy line is sent back through a transformer 276. When the calling subscriber hangs up, the group selector releases and sequence switch 250 moves fo the 17th position. Relay 352 falls back and advances sequence switch 350 to the 10th position, in which relay 360 energizes, releasing relay 372 to prevent the operation of relay 352, so that magnet 361 is restored. Relay 352 energizes, and sequence switch 350 and relay 360 operate in turn until the 17th position is reached, whereupon release proceeds as described above.