Vital interface system for railway signalling

Abstract

An interface system providing vital inputs to and vital outputs from a vital processor of railway signals for railway signalling and control purposes, utilizes non-vital components such as diodes and transistors. The input interface translates a railway signal, for example, from a relay contact closure of a track relay, into a multi-bit serial digital signal representing a restrictive state of the input railway signal in the event of any failure in the input interface. The output interface utilizes an absence of current detector having a saturable transformer coupled to an output line which provides operating current to railway signal and control devices, such as relays, switch machines and signal lamps. A vital relay having a vital driver operated by the processor or control system is operated to drop away upon the detection of a failure, as indicated by the absence of current detectors or in the processor or in the control system itself, to disconnect operating power from the output interface and condition it to provide the restrictive, no-current condition on the output lines thereof.

Dependencies are inferred from the claim text.