GB469664A - Improvements in automatic switches for use in telephone or like systems - Google Patents

Abstract

469,664. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., TAYLOR, R., and BAKER, G. T. Jan. 29, 1936, No. 2705. [Class 40 (iv)] In a selector in which the guard relay B is connected in series with the vertical magnet VM and is short-circuited at each impulse to operate the magnet, the initial operating circuit of the guard relay includes make-before-break contacts a1 of the impulse relay A and a separate non-inductive feed over a rectifier MRA. The circuit of the magnet includes contacts of the change-over relay C which is operated by B so that if the make-before-break contacts remain closed for an appreciable time due to the slow response of relay A on a long or leaky line, the magnet will not be operated. The rectifier MRA prevents the shunt circuit over the non-inductive resistance from interfering with the operation of the magnet. The selector shown has two sets of wipers which hunt simultaneously. On the closure of offnormal contacts N1, relays HA, HB operate and remain locked over their right-hand windings and test wiper P2 or P1 until an idle outlet is found, a self-interrupting circuit for the rotary magnet being closed over front contacts ha7, hb7. If wiper P2 first finds an idle outlet, HA releases removing a short-circuit from C which operates again to switch through the talking conductors and to hold HB over its left-hand winding. If P1 first finds an idle outlet, HB and HA release, C operates as before, and HA is re-operated over its left-hand winding to connect up the upper set of wipers. Busy signalling arrangements controlled by eleventh-step contacts are the same as described in Specification 459,872. Specification 391,123 also is referred to.