We found this circuit in the 1983 Radio Electronics Special projects magazine. The components are common, and the circuit drives a relay. The power supply must be isolated.
Placed in the vicinity of a telegraphic transmitter (CW), this circuit produces an audible signal on...
This circuit provides 2.5 W of power with 6 V supply and 4-ohm speaker. We found it in the Radio...
This circuit was found in Intersil's documentation from the 70's, being indicated for powering...