Patent GB-393111-A (GB)
Title: Circuit arrangement for telegraph exchange systems with relay repeating circuits
IPC: H04L12/04
Filed: 1932-07-25
Abstract: 393,111. Telegraph exchange systems. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. July 25, 1932, No. 20998. Convention date, July 25, 1931. [Class 40 (iii).] Relates to a telegraph exchange system in which signals are repeated through the exchange by two relays, one for each direction of traffic, arranged so that the contact of the relay which transmits to one line is in series with the winding of the receiving relay of that line and vice versa, and in which the operation of the contact of the relay associated with one direction of traffic is prevented from affecting the relay associated with the opposite direction by the introduction of an equivalent circuit which is completed when the transmitting contact changes over. According to the invention, switching devices controlling auxiliary apparatus, such as an exchange printer or clearing lamps, are arranged in the equivalent circuits. When a subscriber TS1 calls by closing his key ET, relay R at the exchange operates and lights a calling lamp (not shown). On the insertion of answering plug ASt into the jack Tk1, relays T1, C1 pull up, switching over the contacts tll, tl2 through which the current flow over the subscriber's loop is reversed. Relay ER then operates, and at contact er energizes relay U which at ul, u2 connects the motor M to the mains N. With the contact u3 closed, the key ET can be released. When the operator has inserted the calling plug VSt into the jack Tk2 of the called subscriber,. relays C2, T2 pull up, and telegraphic communication can begin. With the contact el which responds to impulses from the subscriber TS1, in the position shown, current flows through the lefthand winding of relay MR1, and over the line, loops to the right-hand winding of the relay E2.. When the contact e1 reverses, current flows to the right-hand winding of E2 over a resistance W4 equal to that of the line loop, and relay E2 does not respond. If the exchange operator wishes to record on his printer, he moves one or both of the switches U1, U2 to the opposite position. With the contact el as shown, and the switch U2 in the right-hand position current flows through the left-hand winding of relay MR1 and through the windings of the relay E2 as before. When the contact el changes over current flows to the right-hand winding of relay E2 through the right-hand winding of the relay MR1 and a resistance W6, which, in combination, simulate the resistance of the line loop. Relay E2 is not actuated, but relay MR1 responds, opening contact mrl in the closed circuit of the exchange printer instrument MM. In an alternative form, Fig. 2, relays Al, A2 simulate the resistance of the line loops and contacts al, a2 operate in response to the telegraph signals. When a long (clearing) impulse is transmitted from TS1, contact a1 changes over for sufficient time to allow condenser C1 to discharge, and when al falls back, the charging current operates relay SI, which locks up over c2, s12, and at s11 lights the clearing lamp SL1. In a further alternative form, Fig. 3 (not shown), the resistance of the line loop is simulated by two windings of a relay which is not operated on the telegraphic impulses, but which pulls up on a long (clearing) signal, and effects the operation of a relay which locks up and lights the clearing lamp.