This circuit was originally recommended to give the call signal on intercoms. However, it can be used with other applications. The circuit is from 1978 documentation. The transistor may be the BC548.
Found in an Electronic Design from the 80's, this circuit monitors a three-phase line, activating a...
Relays from 20 mA to 200 mA can be driven by this sensitive circuit.6 or 12 V relays can be used...
All the components used in this 1997 circuit are still common in our market. The circuit must be...