We found this circuit in the May 1996 Electronics Now magazine. The relay must have a voltage according to the circuit power supply and a trigger current of no more than 50 mA.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
This circuit was obtained in an old Elektor. It is a reference, since the integrated products of the...
This circuit was found in a European technical documentation from 1991. It is a circuit that must...