Remote switch position determination using duty cycle modulation

摘要

A system for determining the position of a plurality of remotely located switches having a binary weighted current controlling means connected to each switch for providing a waveform having a unique duty cycle corresponding to the position of each of the switches. The duty cycle is decoded at a local test station to provide digital output data indicative of the position of each of the switches. The duty cycle encoder includes a switching means connected across a two conductor line that terminates the cycle of an input waveform generated by a source generator at said local test station. The current controlling means controls the output of a constant current source which depends upon the number of switches that are open and closed. A timing means is responsive to the output of said constant current source for triggering the switching means. The resultant waveform at the local test station has a duty cycle that is decoded to indicate the position of the remote switches.