335,529. Standard Telephones & Cables, Ltd., (Stevens, C. E., and Hertog, M. den.). June 21, 1929. Automatic exchange systems.-Register-controllers are adapted to take into use an auxiliary register-controller when a call is made requring a number of digits greater than the capacity of the main register-controller. The invention is specially adapted for the establishment of calls between exchange systems in different areas without the intervention of a toll operator or operators. In the system illustrated, the main register-controllers at exchanges within one area are adapted to deal with five-digit numbers comprising one exchange digit and a four -digit subscriber's number. Long-distance calls to another area require, however, two prefix digits, four to six subscriber digits, and possibly one or two additional P.B.X. digits. For such calls an auxiliary register-controller is connected up and after the first four digits have been received by the main register-controller the remainder pass to the auxiliary register-controller. The two prefix digits determine the selection of a junction in the required direction and the remaining digits are then transferred to the distant area in the form of impulses of alternating current over the junction. Since the auxiliary register-controller has to receive a varying number of digits a signal is sent from the main register-controller to indicate the number of main digits to be expected and when the last of these has been received a timing device is energized to effect the switchthrough operations and the release of both register-controllers after a certain delay if no P.B.X. digits are received. If a P.B.X digit is received during this interval the timing device is restarted and a similar test is made for the arrival of a second P.B.X. digit. General arrangement of network. The home area comprises six 10,000-line exchanges arranged in pairs of which both members of a pair are in the same buildings, and 20,000 lines allotted to rural services. The exchange shown in the drawings is assumed to be characterized by a first digit 2, the other exchanges by first digits 3 - - 7, and rural lines by first digits 8 and 9. All the switches used in the conversation circuits are of the 200-point power-driven rotary type. Local calls within an exchange are completed over the five odd levels of a first group selector, a third selector and a final selector. Calls to the other exchange are completed over the five odd levels of a first group selector, a third selector and a final selector. Calls to the other exchange of the pair are completed over the eighth level of the first selector, five levels of a second selector, a third selector and a final selector, the same second selectors being used by both exchanges of a pair for calls to the other. Calls to the other four exchanges in the home area are extended in pairs over the fourth and sixth levels of the first selectors, and calls to rural lines over the second level. Special service calls are obtained by dialling two digits of which the first is 1 and are routed over the tenth level of the first selectors and nine levels of special-service second selectors. Long distance calls are prefixed by two extra digits of which the first 0 denotes the type of call and the second denotes the particular distant area required. The first digit results in the call being routed over the tenth level of the first selectors and the remaining level of the special-service second selectors and the second prefix digit then controls the operation of a special long-distance third selector to select a junction in the required direction. Operation of second finder 2LF and selection of idle main register-control. Battery over cam S, Fig. 1, energizes relays Nmr, Glr, and the latter connects up finder magnet PF. When the calling circuit is found, relay Gtr energizes over cams L, J, and wiper H, releasing relay Glr which closes a circuit over cam K for moving the sequence switch R1 to position 3. Relay Flr now operates over cams E, G, M and back contacts of relays Gtr, Nmr, Rmr and energizes F2r which connects up the register-finder magnet RF. When an idle main register-controller is found, relay Gtr operates again over wiper g, releasing relays F1r, F2r, which move switch R1 to position 4. In the register-controller relay Por, Fig. 3, is connected over cam X to the terminal g, shunt and series resistances, causing the relay to operate slowly. When energized it completes circuits for relays Lbr, Lmr, which also operate slowly. Relay Lmr drives sequence switch' R4 to position 2 and during this movement relay Lmr closes a temporary locking circuit over cam R which supplies the full current to itself and to relay Lbr thus causing the subsequent release of these relays to !be slow. When relay Lbr does release it drives switch R4 into position 5 and by this time relay Isr should have energized over the calling-loop and. wipers a, b. Relay Lbr operates again over cam G and dialling tone is connected up at cam E. Local call; setting of main register-controller. The first digit is repeated by relay Isr over cams P. R. S (of R4) to the counting chain Acr, Bcr, and relay Lmr operates in parallel and moves switch R4 to position 6. At the end of the digit the switch R4 moves to position 8 in which the second (thousands) digit is repeated to the second relay chain Ccr, Dcr. The hundreds and tens digits are similarly recorded on relay chains Ecr, Fcr; Gcr, Hcr, and the first chain Acr, Bcr is then used again for the units digit. When switch R4 moves through position 6¥ after the receipt of the first digit (which in the case of a local call .is 2) relay Lor energizes over front contacts of relays Acr 2.8 and Acr 1.7 and cams M, K (R4). Control of selectors. Switch R5 moves to position 2 from ground over cams B (R5), O, K (R4), and thence to position 3 over cam C (R5) and a front contact of relay RTcr which is energized in series with relay RScr by relay Lor. When the second digit has been dialled the movement of switch R4 to position 10 completes a circuit over cams 0 (R4), B (R5) for moving switch R5 to position 51. In passing through position 4 relay Etr is operated from the counting chain Ccr, Dcr, if the thousands digit is even, and if Etr is energized, a pairing impulse is transmitted to the relay chain Ccr, Dcr, in position 4 of R5 over cam B (R5). Due to the operation of relay Lor, an additional impulse is transmitted to the relay chain in position 4# of R5 over cams T, S (R5) and the result of these pairing and additional impulses is that the call will be routed over one of the five odd levels of the first selector. (If the thousands digit dialled is 0 it is necessary to release the relay chain before it can respond to the pairing impulse and for this purpose relay Por operates and by opening its right back contact causes the locking circuit of the chain to be opened at cam N between positions 9 and 10 of R4). In position 5¢ of switch R5 the fundamental circuit is completed over wiper d, Fig. 1, relay Osr, and cam N(R5), and the front contact of relay Osr is connected over cams F (R4), O (R5) to the relay chain Ccr, Dcr, which responds to impulses sent back from the first selector. When the relay chain is completely saturated a circuit is completed over cam J (R5) for relays RScr, RTcr which move switch R5 to position 6¥ from which further movement to position 7¥ takes place owing to the re-operation of relays RScr, RTcr over cam U (R5). When the hundreds digit has been received, switch R5 moves to position 10 over cams D (R5), 0 (R4), and during this movement relay Ehr will operate over a front contact of relay Efr if the hundreds digit is even and will transmit a pairing impulse to the relay chain Ecr, Fcr. An extra impulse will also be transmitted if the thousands digit was odd over the back contact of relay Etr and cams L (R5), O (R4). In position 10 of switch R5 the fundamental circuit is completed over brushes d, f, Fig. 1, relay Osr, and cam N(R5), and impulses are transmitted from the third group selector until the relay chain Ecr, Fcr is saturated when relays RTcr, RScr drive switch R5 to position 11¢. Battery is now connected over cam M(R5) and brush d to the b-wire and ground over relay Jhr and brush f to the a-wire. Relay Jhr operates over a bridge at the third selector in the hunting position and operates relay Jar which moves switch R5 to position 12¢ and when an idle final selector is found relays Jhr, Jar release and switch R5 moves to position 13¢ over cam N(R4) provided that the tens digit has been received. Tens selection then takes place without translation after which switch R5 moves to position 14¢. When the units digit has been received (on the first relay chain Acr, Bcr) the movement of switch R4 to position 16 completes a circuit over cams N (R4), C (R5) for moving R5 to position 16. If the hundreds digit was even, units selection takes place in the first half of the final-selector bank and the front contact of relay Osr is connected over cams F(R4), O(R5), and a front contact of relay Ehr to the relay chain Acr, Bcr. If however the hundreds digit was odd, the circuit from the front contact of relay Osr goes over a back contact of relay Ehr to the relay chain Ccr, Dcr. An additional ten impulses are therefore introduced since the chain Ccr, Dcr, must be completely set before chain Acr, Bcr is connected up. When selection is completed switch R5 moves to position 18 in which ground over cam T(R5) is removed from brush e thus releasing relay S2r, Fig. 1, and advancing the switch R1. Relays Isr, Lbr release moving switch R4 to position 18. Switch R5 moves to position 1 over cam D(R5) and closes a circuit over cams R(R5), C(R4) for moving R4 to position 1. Call to other exchange in same area. If the first digit is even, i.e. 4 or 6, relay Ttr is energized in position 6¥ of switch R4 and a pairing impulse is transmitted to the