Patent GB-195455-A (GB)
Abstract: 195,455. Siemens Bros. & Co., Ltd., and Humphries, H. E. Dec. 30, 1921. Semi-automatic exchange systems.-An operator s impulse sender is set in accordance with the required number by the insertion of a calling plug in one or more jacks wired to the sender, the plug being then inserted in the jack of a free trunk. The operator's position has ten rows of jacks numbered 0 - - 09, 10 - - 19 and so on. Certain rows may be reserved for calling singledigit and two-digit numbers. To call a line 4567 the operator inserts a calling plug in jack 45, then in jack 67, and then in a jack leading to a selector. The sleeve and ring springs of the numerical jacks are multipled in reverse order to the contacts of the cipher switches CS1 - - CS4 controlled by test relays M, C, T, U and motor magnets DM, DC, DT, DU. The tip springs of all unreserved jacks are connected direct to a relay E, the tip springs of two-digit jacks, such as J80, to relay E through a relay Z1, and the tip springs of single-digit jacks, such as J00, to relay E through relays Z1, L; the relays Z1, L serve to abridge the operations when two-digit and singledigit numbers are called. Setting of impulse sender for four-digit call. On the insertion of plug 16 in a jack corresponding to the first two digits of the wanted line, relays E, EA, DF energize in succession. Relay DF lights the sender lamp 18, short-circuits one winding to mark the sender busy, and earths the three contacts of the plug 16. Relay EA lights the " set-up lamp 19, and closes starting circuits over contacts 6, E (2), ZI(3), for the magnets DM, DC of switches CS1, CS2, which rotate until relays M, C energize over the earthed jack springs. Relay C locks up over winding a of relay G1, which is short-circuited over the jack sleeve spring. When the plug is withdrawn, relay Zl transfers the starting-circuits controlled by relays EA, E to the magnets DT, DU of switches CS3, CS4 so that when the plug is inserted in a jack corresponding to the last two digits, these switches rotate under control of relays T, U until the earthed contacts are reached. The relay U locks up in series with a relay Z2, which energizes when the plug is withdrawn and (1) locks up so as to be independent of relay U, (2) disconnects the " set-up " lamp 19 and lights the " sending " lamp 21, and (3) prepares circuits for the transmission of impulses. Transmission of impulses. On the insertion of the plug 16 in the jack of the trunk to be used, relay SD is energized over the contacts Z2(1), A(l), DF(2), tip of plug, and the a-side of the trunk. Relay SD energizes the motor magnet DSM of the decade switch DS which rotates until its wiper a engages the contact grounded by the relay M of switch CS1. The relay P arrests the switch DS and earths the impulse relay A through a slow interrupter 23. At the first impulse relay A opens the circuit of relay SD, which short-circuits its right-hand winding and closes the impulse circuit from battery over contacts SD(1), P(3), Z2(1), A(1), DF(2), and tip of plug 16 to the selector trunk. This circuit is intermittently broken by the relay A, which flashes the lamps 18, 21 and during each interruption of the impulse circuit energizes the motor magnet DM of switch CS1 over arm b of the switch DS. When the switch CS1 reaches normal, relay M opens the circuit of relav P, which disconnects the impulse relay A. Relay SD again energizes and moves switch DS through a complete cycle, so as to give time for the rotation of the selector, until its wiper a engages the contact grounded by relay C of the switch CS2, when the relay P energizes and impulse transmission is resumed. The tens and units impulses are sent in the same way. Operation for two-digit and single-digit numbers. The insertion of the plug 16 in a twodigit jack J80. say, energizes relay Z1 which disconnects the starting and test circuit of switches CS1, CS2. which do not operate. The decade switch DS moves direct to the contacts corresponding to switch CS3. On the insertion of a plug in a single-digit jack, JOO say, relays L, Z1 are both energized. Relay L opens the holding circuit of the test relay U of switch CS4, and this is restored to normal without sending impulses.