A safety switch with an electronic programmable system including a group of two single-contact relays connected in series, associated with a matching element, a proximity element associated with a support element, magnetic sensors to check the contact status of each of the two relays, two calculation units connected to an exit to the magnetic sensors through the relative control signal connectors and to one entry by a common connector and a magnet associated with the proximity element, with the checking of the status of the relays being managed by the calculation units and taking place by sending a fixed number of fixed-frequency pulse width modulation pulses to the magnetic sensors of each of the single-contact relays and through the connectors and checking the return of the same pulses through the common connector.