GB475419A - Improvements in or relating to telephone systems - Google Patents

Abstract

475,419. Automatic exchange metering systems. AUTOMATIC ELECTRIC CO., Ltd., (in Liquidation), and BEALE, C. E. May 18, 1936, No. 14051. [Class 40 (iv)] In a system in which certain calls are metered in accordance with their duration, the timing apparatus is situated at a central point and sends back A.C. signals over the talking circuit to control metering apparatus at the originating exchange. The invention is described with reference to the control of metering at a sub-satellite. The call is extended via a satellite S, main office M and tandem office C at which the timing apparatus is associated with outgoing junctions together with means if desired for varying the metering charge in accordance with the time of day and for A.C. dialling and other optional features. When the called party replies, timing apparatus, which may comprise a self-starting induction motor or a uniselector stepped by ten-second pulses, is started at the tandem office, and the operation of the back-bridge relay D at the originating office initiates the operation of S and Z relays DA, DB which cause a meter controlling relay J (not shown) to be connected to a source of metering impulses in known manner. At the end of the metering operation DA is released and DB and P are locked-up. Shortly before the end of a unit time period, 800-cycle pips are sent back from Y at the tandem office and ultimately, if the call is not abandoned, a 50-cycle signal is sent from X. Preferably the outgoing circuit is disconnected and bridged while this signal is going back. At the originating office, the signal passes via a low-pass filter F and bridge rectifier MRA .. MRD to AC which shunts out DB. Since D is still operated the next S pulse energizes DA and the meter is actuated again as when the called party replied.