Using the LM3909 this circuit was found in the January 1992 issue of Radio Electronics magazine. Resistor R1 should be chosen according to the table given next to the diagram.
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...