This circuit activates a horn from an audio signal. This can be used for remote control via audio signals. The circuit is from a Radio Electronics from October 1965.
This amplifier with differential input uses two old op amps but can be implemented with modern op amps....
The main feature of this circuit is that it provides a sine waveform signal. In this circuit, the...
The HA2620 integrated circuit used in this comparator is from the 80's, but the setting can be...