Patent ID: 7129703

Claim:
A safety switch with an electronic programmable system ( 2 ) comprising: a group of two single-contact relays ( 9 ) connected in series, associated with a matching element ( 6 ); a proximity element ( 10 ) associated with a support element ( 8 ); magnetic sensors for the check of the contact status of each of the two single-contact relays ( 9 ); two calculation units connected to an output of the magnetic sensors through a respective one of a plurality of control signal connectors ( 15 , 16 ) and to one input by a common connector ( 17 ); and a magnet ( 11 ) associated with the proximity element ( 10 ); wherein the checking of the contact status of the single-contact relays ( 9 ) is managed by the calculation units with the checking occurring by sending a fixed number of fixed-frequency pulse width modulation (PWM) pulses to the magnetic sensors of each of a pair of single-contact relays ( 12 , 13 ) through the connectors ( 15 , 16 ) and by checking the return of the same pulses through the common connector ( 17 ).