GB1149752A - Improvements in and relating to electrical signalling systems - Google Patents

Abstract

1,149,752. Selective signalling. F. C. ROBINSON & PARTNERS Ltd. 6 Sept., 1966 [11 June, 1965; 13 Sept., 1965 (2)], Nos. 24852/65, 39035/65 and 39036/65. Heading G4H. In a signalling system a plurality of pairs of transmitter units and receiver units distributed between a local and a remote station are coupled together sequentially over a single channel in a time-division manner and the system is characterized in that (1) at the local station a master clock advances an eight-stage master binary, counter, the eight-bit output from which sequentially readies the units at the local station, (2) at the remote station an eight-stage slave binary counter is advanced by clock-pulses transmitted from the master clock so as to ready sequentially the units at the remote station and (3) synchronization is maintained by causing the master counter to inhibit the transmission to the remote station of the last eight clock-pulses in each cycle of 256 clock-pulses determined by the master counter, which synchronizing gap when detected at the remote station causes the slave counter to be reset to zero in readiness for the start of the next cycle. As described each transmitter can transmit a single bit in accordance with the position of a switch contact and each receiver controls an indicating lamp via a relay which could also control remote machinery. The system described is particularly adapted for use between a mine and the surface in that a plurality of failsafe features are incorporated. Outline circuits of conventional transistor gating and switching units are given.