This circuit was found in the July 1978 issue of Radio Electronics magazine. The circuit uses a common digital voltmeter as the indicator. The sensors are integrated circuits of the time.
Suggested by Motorola documentation from the 1980s, this circuit can be implemented with...
This oscillator reaches 50 MHz with an overtone crystal. The circuit is from Electronics Now...
This modulator circuit for low intensity signals is from old documentation. The integrated circuit...