This adjustable frequency circuit was found in December 1986, Radio Electronics magazine. The base frequency is given by C1 and the power supply must be 5 V.
This circuit is used to obtain the synchronized activation of a mechanical battery clock. The...
ON Semiconductor Phototransistor Output Optocouplers Available from Mouser Electronics is the...
Found in an Electronic Design from the 80's, this circuit monitors a three-phase line, activating a...