Interlock switch circuit with single fault detection

摘要

A testing system to test safety interlock switches to ensure that they are operating normally comprising a test loop circuit 16 which connects in series a plurality of safety switches 2, the test loop circuit 16 is adapted to open the switches 2 outputs if broken, the testing system further comprising a diagnostic means 18 which checks each switch to ensure it is operating normally when the test loop circuit 16 is broken. The test loop circuit 16 may be broken when a single switch 2 is activated to open its safety output.