Circuit for detecting wire contacts and incidence of external voltage

摘要

A test relay (P) having two windings, through which an equally large current flows in opposite directions when the load is disconnected, is connected in series or arranged in parallel with the load (V) of the circuit to be monitored. In the event of a wire contact or incidence of external voltage, one of the windings is in each case short circuited and the test relay operates. To test the operation of the test relay, a connecting routine is provided in which it is checked whether the test relay can operate both via one and the other winding. <IMAGE>