This circuit serves as an audio output for AM or even FM radios and was found in a Radio Electronics magazine from March 1990. Note the supply voltages.
We found this circuit in an old QST magazine. The circuit is powered according to the thermostatic relay...
This circuit was found in a 90s Popular Electronics. The components are from the era. R3 must be...
Found in a 1968 EEE, this circuit accepts frequencies from 1 to 1000 Hz and control voltages from 0.1 to...