A simple circuit with which we have the
possibility opening and closing the RL1 contacts. He becomes touching a small metal
surface. Clue of situation that is found RL1, is become by the Led D3. The supply of
circuit is +12V, the IC1 is supplied with 3.9V fall of voltage that is ensured by
combination R5 and zener D2. For more good
restoration perhaps it should adaptation of R1 value.