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 was found in Electronics Now. With it the dialing signals of a telephone are...
This traditional configuration of a white noise generator that uses the junction of a transistor with a...
This circuit generates an accurate 1 Hz signal controlled by a crystal. The circuit is from 1995...