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 generates signals from 0.01 Hz to 10 kHz, but uses unusual components today. The...
This 1969 Mullar circuit appears elsewhere on this site. The circuit uses germanium diodes and the...
This control circuit for direct current motors uses a 741 and an operational one of unusual power...