225,703. Coventry Automatic Telephones, Ltd., and Collyer, J. E. Dec. 4, 1923. Automatic exchange systems; metering systems.-In a registercontroller of the code-translating type, the dialling of the exchange letter causes a relay in each of two groups of multi-contact relays to lock up and select the office code to be sent. The transmission of impulses is effected by an interrupter under control of a relay counting chain. Provision is made for release of the register-controller if dialling is delayed or prolonged, for connection to operators in response to the digit O or to a non-existant number, and for freeing the line from a faulty register controller. In the system described, Strowger selectors are controlled by impulses over one talking wire, but the invention is applicable to systems using loop impulsing and power-driven selectors. General operation. A subscriber A, Fig. 1, on calling is connected by his line switch B to a relay group C, Fig. 2, associated with a selector F and a hunting switch D which picks up an idle register-controller, Figs. 3 - - 5. These figures should be read as one, Fig. 4 being arranged to the right of Fig. 3 and above Fig. 5. The first three letters of the exchange name are recorded on registers K1 - - K3 which are connected up in succession.by a switch L. The setting of registers K1, K2, causes the operation of a particular relay in a group N of " primary relays " and the setting of registers K2, K3 determines the operation of one of a group P of " secondary relays." These relays lock up and the registers K1 - - K3 are released. The thousands digit operates a register K4 and the remaining digits re-operate registers K1 - - K3. The operated primary and secondary relays jointly pick out a particular group of terminals on the left of a frame Q on which cross-connections are made to bus-bars going to the relays of a counting-chain R. Particular relays of the chain are thus marked in succession by the switch M (which moves on after the sending of each digit) and control the number of impulses sent by an interrupter 301. Selection of idle trunk and non-faulty registercontroller. The line switch B operating as in Specification 208,075 seizes an idle relay group C similar to that described in Specification 223,385 whereupon relays 51, 57 pull up and complete a hunting circuit for magnet 60 of switch D. When an idle register-controller is found, relay 69 is no longer short-circuited and extends the in-and-out sides of the lower talking wire over wipers 64, 65, connects relay 77 to wiper 66 and opens the circuit of sluggish relay 57. Normally, the seized register-controller returns ground over wiper 66 to lock up relay 69 and energize relay 77 which then locks and holds the connection. If, however, this does not happen, the relapse of relay 57 releases relay 69 and the driving magnet 60 is energized from ground' at its off-normal contact 63. Relay 57 re-energizes somewhat sluggishly and hunting then proceeds in the ordinary way. Registration of office code. As soon as relay 69 operates, dialling tone is sent from 107, Fig. 3, over relays 105, 80 and both these relays pull up. Relay 108 now energizes over wiper 201 of switch M, and energizes relay 111 which returns a holding ground as mentioned above. The first digit is repeated by relay 51 to relay 105 which repeats it over wiper 203 of the switch L to the driving magnet 202 of the register K1. At the first impulse, relay 116 energizes relay 120 which locks up and substitutes a direct ground for the dialling wire 107. At the end of the digit, relay 116 falls back and releases the closing magnet 208 (which it previously energized) to cause the switch L to advance one step. The second and third letters are recorded on the registers K2, K3 and the switch L then moves to its fourth position in which relay 123 is energized over wiper 219 and connects ground to wipers 209, 221 of the register K2 and battery to wiper 213 of register K3. Wiper 204 of register K1 connects battery to all the primary relays associated with the digit by which it is set and wiper 221 completes the circuit for the particular relay associated with the second digit. Wipers 209, 213 similarly prepare a circuit for a relay in the secondary group P. As shown, the primary relay 215 operates and completes the circuit of the secondary relay 217. Both relays lock up to ground controlled by relay 111. Relay 215 closes a number of groups of contacts leading to terminals on the frame Q and relay 217 extends one of these groups back to terminals engaged by wiper 253 of the switch M. Registration of numerical code. The thousands digit is recorded on the register K<4>. The energization of relay 116 at the beginning of the digit energizes the release magnets 240 - - 242 of the registers K1 - - K3 over wiper 219 and front contact 129 of relay 123. At the end of the digit the switch L takes a step as usual, relay 123 falls back and the remaining digits successively operate registers K1 - - K3. Transmission of office code. The operation of a secondary relay grounds the wire 247 so that relay 304 pulls up over the sending interrupter 301 and locks itself in series with relay 302 which pulls up as soon as the interrupter breaks contact. Interrupter 301 is now connected to relay 130 which at its upper armature repeats the impulsesover wire 102 to the lower outgoing talking wire- and over its lower armature to the counting chain R. The first energization of relay 130 energizes. relay 305 over 249 and the following relapse energizes relay 321 over 251. The next impulse energizes relay 306 which releases relay 305 and the next space energizes relay 323 which unlocks relay 321. Relays 305 - - 314 thus energize in succession and relays 321, 323 alternately until the relay that is marked over wiper 253, the secondary and primary relays and the frame Q, is reached. This relay on energizing extends the marking ground over contact 329, or 341 to relay 303 which disconnects interrupter 301, unlocks relays 302, 304, and locks itself under control of relay 333 which was energized on the first energization of relay 321. Relay 302 unlocks the operated counting relay. On the relapse of relay 304 relay 333 falls back slowly and releases relay 303. Driving magnet 256 of the switch M which energized when relay 303 pulled up is thus released and the switch moves on to transfer the marking ground over wiper 253 to the next of the group of terminals on the frame Q. Relays 302, 304 lock up again and a second digit is sent in a similar manner. In the system shown, the maximum number of digits in the translated office code is 4. If fewer than four digits are to be sent, certain of the terminals are jumpered to the terminal O on the right of the frame Q, and when the marking ground is transferred by switch M to such terminals, relay 303 energizes immediately over wire 273 and releases, and is released by relay 304 so that the switch M takes another step without any impulses being sent. Transmission of numerical code and release of the register-controller. In positions 5 - - 8 of the switch M the wiper 253 is connected in succession to the wipers 58 - - 261 of the registers. K4, K1 - - K3 the banks of which are multipled to the counting relays so that the number is sent out without translation. After the final digit, wiper 201 moves to a dead terminal and relay 108 fall back and releases relays 120, 111. Relay 120 energizes the release magnets 266, 264 of the switches M, L, and, when the switch L reaches normal, the release magnets 240 - - 242 and 268 of the digit registers. Relay 111 releases the primary and secondary relays, takes the busy mark off the register-controller and releases relay 69, Fig. 2, so that the talking wires are switched through. Group selector F, Fig. 2. As soon as relay 69 connects the out side of the trunk to wiper 65, relay 402 pulls up and energizes the sluggish relay 412. Relay 402 repeats impulses from the register translator to vertical magnet 403. The change-over of vertical springs 409 causes relay 412 to fall back at the end of the digit and energize the rotary magnet 404. The change over of rotary springs 410 puts the rotary magnet 404 and switching relay 420 under control of the test wiper and the selector hunts for an idle line completing a local circuit for itself at each step as described in Specification 219,453. Incoming selector G and second selector H, Fig. 6. When the selector G is picked up over one or more selectors such as that just described, relays 451, 454, 455 pull up. Relay 451 repeats the thousands digit to vertical magnet 460. The change over of vertical and rotary springs 456, 466 cause the relapse of relay 455 at the end of the digit and the completion of a hunting circuit as in the selector F. When an idle selector H is found, relay 476 pulls up in series with relay 501. In this selector the operation of switching relay 469 does not release the line relav 451 which repeats impulses to subsequent switches. The selector H is identical with selector F. Connector J, Fig. 7. Relay 552 energizes over the release wire and is followed by relay 557, impulse relay 561 and sluggish relay 564. The tens digit is repeated by relay 561 to the vertical magnet 567. The change-over of vertical springs 554 causes relay 564 to relapse at the end of the digit so that the final digit goes to the rotary magnet 569. The change over of rotary springs 559 ensures the successive relapse of sluggish relays 552, 557 at the end of the digit. Busy signal. If the line is busy, relay 570 pulls up and is locked by the relapse of relay 552. When relay 557 falls back, busy tone is sent from 575. Ringing current and signal and supply of talking current. If relay 570 does not pull up, the relapse of relay 552 energizes switching relay 570 and the subsequent relapse of relay 557 sends out ringing current from 583 over the trip relay 58