GB403508A - Improvements in or relating to telephone systems - Google Patents

Abstract

403,508. Automatic exchange systems. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, and PUCKETTE, C. C., c/o General Electric Co., Stoke, Coventry. Oct. 25, 1932, No. 29836. [Class 40 (iv).] In an arrangement in which current is supplied to a sub-exchange over a junction from the main exchange either normally or in exceptional circumstances, the comparatively heavy current necessary for driving switches is obtained by the use of a motor connected to the junction and provided with a flywheel or other energy-storing device so as to act for short periods as a generator. The motor is preferably of a high-speed permanent-magnet type having a low resistance armature. In Fig. 1, current is received over the junction 4, 5 or over a single wire with an earth return. The switches are connected to leads 2, while the various relays are connected to leads 3. As long as the sub-exchange is in use, relay X is operative and connects current to the motor M, which by virtue of the stored energy in its flywheel acts as a generator when the switches draw current from leads 2 and maintains the voltage for a sufficient time for their operation. Alternatively, the motor M may be started only when impulsing is about to take place. In Fig. 2, the current is normally obtained from the local A.C. supply 12, relay Y being operated thereby. Upon failure of the supply however, relay Y falls back and current is received over the last-choice junction 6, 7, which is marked busy at both ends, and lamp AL is lighted at the main exchange. The motor M is started, and acts as a generator when comparatively heavy current is required as in Fig. 1. If desired, the current from the main exchange may be received over several junctions in parallel. The arrangement may be employed to supplement a local battery in the event of failure of the charging plant or excessive discharge of the battery. Specification 388,935 is referred to.