PROVING SAFE OPERATION

摘要

A method of proving safe operation of a complex electronic circuit (2), and apparatus for carrying out the method, in which a proving signal having known characteristics is superimposed on an input (4) to the circuit (2) and the output is searched for said characteristics. An example involves the use of a microprocessor (2) arranged to evaluate a fast Fourier transform algorithm on the coded carrier signal (4) of a railway automatic train protection system or of railway a.c. track circuit arrangement.