GB1208100A - Improvements in or relating to telecommunications exchange systems - Google Patents

Abstract

1,208,100. Automatic exchange systems. SIEMENS A.G. 1 Aug., 1969 [2 Aug., 1968], No. 38593/69. Heading H4K. Should a junction to a satellite exchange be held as the result of a false response or a fault at the satellite, forced release is effected from the main exchange by charging a capacitor in shunt across the junction at the satellite so that discharge of the capacitor effects loop disconnection and diversion of the junction to the satellite control circuit, the time constant of the capacitor charging circuit being sufficiently high to prevent operation of the circuit in response to ringing. As shown in Fig. 1 a subscriber Tn at the satellite with network KE is accessible over a junction HL from a main exchange Vst, the junction being terminated at the satellite on a circuit BS that can effect forced release and diversion to control circuit ES in receipt of switching instructions over one or other of the junctions such as HL. If the junction is held by low impedance, either presented from a subscriber or by a fault which loops the line, main exchange Vst effects release by connecting earth at f1 so that shunt capacitor C1 charges at BS to the small residual voltage across the loop. When charged, f1 is released and C1 discharges with transistor T1 providing a discharge path through relay A a contact of which breaks the loop. With the loop broken a positive potential is applied from f2 at Vst to charge a shunt capacitor C2, charging of which up to this time is prevented by Zener diode 8. With f2 broken, discharge of C2 operates relays A, B and C, in series to complete diversion to control ES and release the network KE. An alternative arrangement, Fig. 2, not shown, places all three relays A, B and C under control of the discharge current, of capacitor C2, a fourth relay (H) effecting disconnection of the loop in response to discharge of capacitor C1. By this means the diversion contacts a, b can be positioned at the satellite side of circuit BS and earth pulsing of one leg is sufficient to effect control if operation of relay (H) diverts the leg to an otherwise disconnected shunt capacitor C2.