Model railway control system - has three level track voltage switching which reverses voltage to transmit data and switches it off for clock pulse

摘要

All the trains, signals etc., in a model railway are powered and controlled by a central, unit which continuously switches the track voltage between OV and either + or -12V. +12V represents binary 'O', -12V represents binary 'l' and each bit is preceded by a short clock pulse at OV. A rectifier in each train etc., recovers a DC supply from the track voltage. It is chopped by the clock pulses and may be smoothed if necessary. Control data words, e.g. 6 bits are sent to data receivers in all trains etc., as a continuously repeated time-multiplexed sequence. The start of a sequence is identified by a synchronising word. Each receiver contains a data decoder which extracts its own word from the sequence and decodes the instruction.