Patent GB-767397-A (GB)
Title: Telephone systems with a main exchange and a satellite exchange
IPC: H04Q3/00
Filed: 1953-03-27
Abstract: 767,397. Automatic exchange systems. LICENTIA PATENT-VERWALTUNGS-GES. March 27, 1953 [April 1, 1952; April 1, 1952], No. 8530/53. Class 40 (4). In an automatic satellite (non- exchange) which is connected by a plurality of junctions to the exchange from which it receives all current the talking circuit of a completed connection has no current consuming components such as relays and rectifiers in or connected to it unless they be short circuited. Release is effected by current reversal acting on a relay connected in series with a rectifier across the line wires. Relays A, B, in the satellite, Fig. 1, and A1, B1 in the exchange, Fig. 2, are normally operated. Outgoing call. The closure of the loop by the calling subscriber Tn1 earths a common start lead An to bring up a relay D associated with a free junction AL. Relays A, A1 release, the former connecting the relay selector RW to the wire a and the latter energizing relay W in the exchange. A marginal relay T operates and a circuit is completed from earth in the relay selector RW to operate an impulsing relay J and V follows to connect up the driving magnet AW of a switch aw. The impulsing relay J stops the relay selector RW and the switch aw in synchronism. The off-normal contact rwo of the relay selector RW removes the shunt on M. When the calling time is reached, a test circuit Pr, including an opposed winding of relay B, is completed whereupon B releases and disconnects the relay selector RW. The operated line connecting relay I (not shown) of the selector RW holds due to the remanence of its magnetic circuit. At the exchange switch aw has connected up the meter and, providing a final selector LW has not been set to an outlet corresponding to the caller, completes over wipers aw3, aw4 a circuit for relays C, K which disconnect the control circuit and, together with T1, switch the junction AL through to the group selector GW. Relays M, D at the satellite fall back. Relay A is energized by the feeding current applied to the line wires at the group selector, and removes a short circuit across F which operates to release A. Relay F holds due to the remanence of its magnetic circuit. The caller then completes the connection. Release. When the caller replaces his receiver, the group selector GW and the preselector VW return to normal whereupon an opposed winding of W is energized. Relay W falls back followed by C, K which effect reversal of the feeding current by connecting negative potential and high resistance earth to the wires b, a, respectively. Relay T pulls up to connect low resistance earth to the wire a. This step-by-step current reversal is to ensure that the subscriber's bell is not sounded by rapid discharge of the condenser in the bell-set. An opposed winding of F connected in series with rectifier GRII across the line wires is energized. Relay F in releasing connects up M and shunts one of the opposed windings of B1 which connects negative potential to the wire a. Relays A1, A, B operate and the relay selector RW and switch aw are homed, whereupon M releases. Incoming call. If the called subscriber is free, relay E associated with a free junction operates when the final selector LW is set. Relay G breaks the circuit over the wire a to release A, A1 and marginal relay T operates. The impulsing relay J steps the selector RW and switch aw in unison until, when the latter reaches the outlet marked by the final selector LW, relay C operates to disconnect the impulsing circuit together with relays B, B1. When the called party answers, relay A brings up F and then releases. Relay F connects its opposed winding across the line wires. When the connection is released, F is de-energized by the current reversal to return the satellite to normal as described above. In a modification, Fig. 3 (not shown), the release relay F normally holds due to remanence. When during a call the subscriber's line is connected to a junction, F is released, but when through release of the connection current reversal occurs, F operates and returns the satellite to normal. In a further modification, Fig. 4 (not shown), the release relay F energizes when the loop is closed, short circuits its energizing winding and holds due to remanence. Specifications 719,656, 741,364 and 759,589 are referred to.