We found this circuit in the March 1995 issue of Electronics Now magazine. The circuit has a frequency range determined by C1 and R3. The signal generated is square.
This circuit is from a 1965 General Electric publication. It uses a thermistor to fire a reed...
This circuit was obtained from the PE Hobbyist Electronics publication of 1980. The circuit is...
This Vox or sound activated relay was found in an American documentation from 1975. Equivalent...