This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can be adapted to use an LED or audible indicator instead of a light bulb.
This setting appears other times in this section from other sources. This is from an 80's American...
This digital timer provides timings from 1 minute to 10 hours with indication on a 3-digit...
Signals from 27 MHz to 150 MHz can be produced by this one-transistor oscillator. The frequency...