209,017. Western Electric Co., Ltd., (Assignees of Carpenter, W. W.). Dec. 22, 1922, [Convention date]. Automatic exchange systems.-A system is described in which selectors of Strowger type, but of 200-line capacity and having in some cases two sets of wipers, are controlled by a register-controller which on the one hand translates the twodigit designation of the wanted exchange into a routing-number which may comprise any number of digits up to five, and on the other hand translates the four-digit number of the wanted subscriber into a five-digit non-decimal equivalent suitable for operating the largecapacity selectors. If the call is a local one the register-controller merely suppresses the exchange digits. A calling line is connected by a Strowger call-finder having two sets of wipers, Fig. 1, to a group selector, Fig. 2, whence a lateral connection is made by a similar callfinder, Fig. 3, but having only one set of wipers, to a register-controller, Fig. 4, comprising three Strowger registers. The first register, which is set by the two exchange digits, comprises six banks 1 - - 6. The first bank 1 has its terminals jumpered to the first bank of a switch s<1>, s<2>, s<3>, to determine how many digits up to a maximum of five the routing-number shall contain, while the banks 2 - - 6 determine the values of these digits by the way in which their terminals are jumpered to ten wires corresponding to 1, 2, 3, &c. outgoing impulses, the wipers 410 - - 414, or some of them, being brought into circuit in turn by the wiper s<3> to effect the consecutive sending of the digits. In the same way the wiper s<3> afterwards brings into circuit the wipers 415, 416, 4] 7 of the second register, which was set by the thousands and hundreds digits, and then the wipers 418, 419 of the tens and units register. The bank terminals of these registers are jumpered so as to effect the necessary non- decimal translation. Thus the first selector at the wanted exchange must pick out a group of 2000 lines, and the wiper 415 accordingly determines the sending of one impulse if the thousands digit is 1 or 2, two impulses if the thousands digit is 3 or 4, and so on. The second selector picks out a group of 200 lines, and the wiper 416 therefore effects the retransmission of the hundreds digit unmodified. The connector has two sets of wipers one or other of which must be brought into action accordingly as the thousands digit was odd or even, and this is effected by the sending of either one or two impulses under control of the wiper 417. The tens and units digits are then retransmitted unmodified, under control of the wipers 418, 419, to effect the vertical and rotary movements of the connector. The digits from the register-controller first operate the selector shown in Fig. 2, and then extend the connection over a number of two-wire inter-exehange trunks, each having a repeater, Fig. 2, at the outgoing end and a selector, Fig. 5, at the incoming end, until the wanted exchange is reached, where the connection is completed by selectors. Figs. 5 and 6. and a connector, Fig. 7. The selector shown in Fig. 6, like the call-finder, Fig. 4, and the connector, has two sets of wipers. As soon as the connection is completed the register-controller is released and the circuits are switched through. Strowger call-finder with two sets of wipers, Fig. 1. The operation is illustrated in connection with substations X and Y which are respectively accessible through the upper and lower sets of wipers. The line relay 161 or 163 energizes a subgroup relay 100, which locks itself, energizes relay 102 to open its original circuit, grounds a terminal 103 in the path of an auxiliary vertical wiper, and closes a circuit E, 108, 106, 105, 134. Relay E closes a branch circuit through the vertical magnet 109, which opens the circuit of relay E, so that a hunting action ensues, the relay E and magnet 109 energizing and de-energizing each other in turn until the wiper 112<1> arrives on the marked terminal 103, whereupon relay A becomes energized in series with relay E. Relay A locks itself, opencircuits the vertical magnet, and energizes relay B. A sluggish relay C that was energized in series with the vertical magnet now relapses and closes a circuit 110, 116, 108, 106, 105, 134 to energize the rotary magnet 110, which steps the wipers to their first terminals and de-energizes relay E. The wires 124, 129 of non-calling lines are grounded, so that if the two lines now under test are both non-calling the relay B remains energized in circuit 118, 120, 124 and relay E is energized over circuit 108, 111, 126, 127, 129. In this case the relay E again energizes the magnet 110 to advance the wipers another step, and the relay E and magnet 110 continue to interact to rotate the finder until the ungrounded wire 124 or 129 of the calling line is reached. If it is the substation X that is calling, the wire 123 is grounded and keeps the relay B energized but the wire 129 is not grounded and no longer shortcircuits a relay D. which hecomes energized in a circuit 133, D. 111, 108, E. The relay D opens the rotary magnet circuit, locks relay B, extends the starting-circuit 134 over wire 143 to the next idle finder, and grounds the wiper 130 to mark the substation X non-calling and to energize its cut-off relay 162. The relay 162 locks itself and short-circuits the left-hand winding of relay 161, which relapses and de-energizes relays 100, 102. If on the other hand it is not the sub-station X but Y that is calling, there is no ground on the wire 124 and relay B relapses, bringing into action the lower set of wipers and connecting wire 127 to wire 121 so that relav D is no longer short-circuited and operates as described before. The relav D locks itself through its lower winding to the starting circuit 134, so that when the calling subscriber disconnects himself the relay D remains energized if and as long as the circuit 134 is grounded, i.e. while a subsequent finder is hunting. Strowger call-finder, Fig. 3, for connecting an idle register-controller. This is started by the closing of the off-normal contact 133, Fig. 1, and operates like the call-finder shown in Fig. 1 except that it has only one set of wipers. The energization of relay 212 removes ground from the terminal 331 to mark it calling. When the wiper 330 reaches this terminal it grounds it and energizes relay 211, which switches the calling line over wines 262, 263 to the line relay 436 of the register-controller. Operation of register-controller, Fig. 4, by dialled digits. The line relay 436 energizes relay 439. The two digits representing the wanted exchange and the four digits of the called number are repeated over the switch-arm a<1> in successive positions to the vertical and rotary magnets 400, 401, 403, 404, 406, 407 of the three Strowger registers. At the end of each digit a sluggish series relay 442 relapses and de-energizes magnet a to move the switch a<1>, a<2>, a<3> a step forward. Emission of translated digits by register-controller. When the arm a<3> reaches its third position, i.e. as soon as the two exchange digits have been registered,. it closes a self-interrupting circuit for the magnet s, which hunts the switch s<1>, s<2>, s<3> until the' arm s<1> finds the terminal grounded by the wiper 409, whereupon relay 447 becomes energized, locks itself, and closes a non- interrupting circuit for the magnet s. This hunting movement is governed by the way the terminals of the' bank 1 are jumpered to the arc of the arm s<1> and determines how many exchange digits shall be emitted. For example if five such digits are necessary for a particular call the switch s<1>, s<2>, s<3> only hunts a single step, while if four exchange digits are necessary the switch hunts two steps, or if the call is for a subscriber on the same exchange as the calling subscriber, so that no exchange digits are required, the switch hunts six steps, bringing it at once to the position for transmitting the first of the five digits corresponding to the wanted subscriber's translated number. It will be assumed that five exchange digits must be sent, so that the switch s<1>, s<2>, s<3> moves only to its second position. The relay 447 connects an interrupter 450 to relay 449 which energizes relay 448. Relay 451 becomes energized in series with relay 449 at the next opening of the interrupter circuit and connects the interrupter to relay 453, which, in response to each subsequent impulse, energizes relays 428 and 452 and the stepping magnet c of a switch c<1>, c<2>. The relay 452 locks itself to wire 454 and repeats the impulses over wire 460 to the vertical magnet 240 of the first selector, the locking circuit 454 being opened at each impulse by the armature of the magnet 240 when it completes its stroke. When the arm c<2> reaches the terminal grounded bv the wiper 410 it energizes relay 426, which stops the digit by disconnecting the interrupter 450 from relay 453, connects the interrupter to magnet TM to step a timing switch TM<1>, locks itself up over a contact of the sluggish relay 428 and over the off-normal arc of the switch TM<1>, and unlocks relays 449, 451. Relay 449 de-energizes magnet s, which moves the switch s<1>, s<2>, s<3> to its next position, grounding wiper 411 instead of 410. When the timing switch TM<1> regains its normal position it unlocks relay 426, which again connects the interrupter 450 to relay 449, and a second digit is transmitted in the same way as the first but under control of wiper 411. Subsequently three more exchange digits are sent in the same way under control of the other three wipers 412, 413, 414 of the exchange register, the number of impulses in each digit being determined by the way the terminals of the banks 2 - - 6 are jumpered to the arc of the switch-arm c<2>. Finally, in the seventh to eleventh positions of the switch s<1>, s<2>, s<