Found in a 1980s documentation, this circuit uses transistors from that time. Modern equivalents can be used. The alarm is a piezoelectric buzzer with na included oscillator.
This circuit serves to receive optical signals modulated in amplitude providing an audio signal at its...
This microphone preamplifier can be used in a variety of applications. The circuit is from a Radio...
This circuit using an operational amplifier was found in old American documentation. It can be...