887,977. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. July 29, 1958, No. 24344/58. Class 40 (4). A multiple regenerator for use in an automatic telephone system comprises a circulatory serial store in which data is stored as a number of binary elements, a section of the store being allocated to each of a plurality of auto-to-auto relay sets, the arrangement being such that each digit of a number of digits to be transmitted is received at a relay set, recorded in a receive portion of the associated store section, transferred therefrom in a plurality of transfer operations to a control portion whence the digit is retransmitted. Reception and retransmission for a particular relay set may take place simultaneously, and operations may be in progress for any one or more of said relay sets during the same cycle of the serial store. As described, the serial store comprises a nickel wire sonic delay line having 520 pulse positions divided into 13 groups each of 40 positions, each group being allocated to one of twelve sequentially-scanned auto-to-auto relay sets, except for the thirteenth group, which is used for synchronizing and counting functions. When a line is looped a relay set and associated regenerator are seized. The first impulse enters a " chalk mark " in the first position of the related group. By counting the number of store cycles which occur during an impulse, the attainment of a sufficient count in the 13th store section distinguishes true impulses which last for at least 8.33 m.secs. from spurious impulses. When a pulse has been detected as a true break impulse, unity is added to the contents of a block of four pulse positions in the relay set's store section. At the end of the break impulse, the loop is remade and the " chalk mark " cancelled, a further timing operation for the period for which the loop is closed then taking place. If the make persists for at least 116 ms. it is assumed to be an inter-digital pause and not an inter-impulse gap. The store section which forms the regenerator for a relay set also includes a number of groups of pulse positions called digit stores. When an interdigital pause has been detected, the digit which has been stored in the receive position is transferred in complement form to the first digit store, the transfer being effected by passing a delay device which interconnects the reading and recording devices. In the same cycle, the receive positions are cleared to receive the second digit. In subsequent cycles the digit passes along the sequence of digit stores until it reaches the first digit store. The process described above is repeated for each digit. Regeneration.-When a recorded signal indicating that an impulse has been detected is read by the delay line's reading device, the associated relay set seizes its outgoing loop by closing it. When the first digit, as a result of transmission down the line, reaches the sending position, transmission thereof commences. Control of the duration of the regenerated impulses is by a transmission " chalk mark " which is advanced along the line once every 33.3 ms., the length of an impulse being fixed by two such shifts, unity being added to the contents of the sending control position when an impulse is sent so that, since the digit has been complemented, the attainment of " 1111 " indicates that the digit has been sent. The inter-digital pause is timed by counting in a block of four pulse positions initially at zero, counting commencing when all transmission marker positions are blank, after the last impulse of a digit has been sent, and proceeding for sixteen periods each of 33.3 ms. A transmission marker shift sequence of six shifts then occurs. Subsequent digits are transmitted similarly. Impulse reception and transmission can occur simultaneously. Timing control, Fig. 2.-A one-megacycle crystal-controlled oscillator XO drives a pulseformer PF, the pulses P from which drive a set of counters CA, CB, CC, the scale-of-five counter CA being stepped by each P pulse, the scale-ofeight counter CB being stepped by each fifth P pulse, the scale-of-thirteen counter CC is stepped by each fortieth P pulse and controls scanning of the various relay sets. Synchronization between the store circulation and the waveform generator is as described in Specification 781,902, and employs an A.C. current to control the temperature of the nickel wire. Relay set, Fig. 1.-There is one auto-to-auto relay set per outgoing junction arranged as shown in Fig. 1. When the set is seized by a selector a relay A operates and operates a relay B. The relay B locks up, busies the relay set, extends the connection to the junction and removes the " clear " condition to the regenerator. Relay A repeats loop impulses to the multiplex input to the regenerator. As soon as the regenerator receives the first impulse, energization of the OP input operates a trigger TC1 to energize a relay BY, which then short-circuits relays D and I to present a constant impedance to incoming pulses and connects an impulse contact ip1 to the outgoing loop. When all digits received by the regenerator have been retransmitted, the relay BY is released and connects the speech path to the outgoing junction. When the called subscriber replies, the potential on the line is reversed to operate the relay D, so preventing further input to the regenerator even if the relay should be momentarily released during the call. At the completion of the call, the calling subscriber hangs up, thereby releasing the relay A and hence the relay B. Store circulation circuit.-Intelligence passes along the delay line SD, Fig. 4, and is continuously read by a coil RC. Outputs R0, R1 from the reading amplifier are energized for a 0 and 1 respectively. In the quiescent state of the store, the R1 output is fed via a gate G401, delays 41D and 42D and a gate G407 to a recording amplifier WA. This process is called " copying." The gate G411 prevents copying of the first pulse position of the relay set's regenerator. Addition is controlled by a bi-stable device 52F (Fig. 5, not shown) which controls gates G401, G402, the inverter output R0 being passed through G401 until the first zero is read, when a bi-stable device 54F (not shown) is reset to close G403 and open G402. The transfer operation is controlled by a bi-stable device 51F (not shown) which controls gates G408, G409, G408 permitting normal transfer, and G409 permitting transfer of a digit with complementing from the receive position to the first digit store. Marker pulses are transferred without complementing by gates G416, G417. A gate G405 causes 1 to be recorded in position 5 when the receive time scale makes its first count, and a gate G410 causes " 1 " to be recorded in pulse position " 36 " of the regenerator as a transmission marker when the interdigital pause counter has completed its count. Gate G407 is closed when there is an output from any one of the gates G412-G415, these gates being arranged to clear the output digit position, clear the receive time scale, clear the whole regenerator and clear pulse position " 6 " of the regenerator.