Fail-safe command signal transmission device - enables fast response with low frequency pulses via two parallel lines

摘要

The sending end consists of two EXCLUSIVE-OR gates fed from a pulse generator and feeding two monostables. The second input to the OR gates is connected to the command source and is quiescent at a positive voltage. The two pulses generated have coincident back-edges, are of different widths, and are negative. The OR gates thus act as inverters. The monostables generate narrow pulses from the front-edges and these are thus not coincident. The receiving end consists of an AND-gate feeding a re-triggerable monostable which is set for a reset period longer than the period of the pulses. The two lines are also connected to a lamp indicator to monitor the transmission of pulses. When the command input goes negative the OR gates cease to invert and the monostables are triggered by the positive pulse rear edges.