Unijunction metronome (CB21701E)

This traditional metronome circuit is powered by voltages from 9 to 12 V and output drives a common speaker.

Single crystal radio (CB22170E)
Found in English documentation from the 1980s, this circuit can use any germanium diode. The...
Pocket Rhythmizer (CB12358E)
This circuit can be used to set the compass for walks or exercises, being small enough to be...
Oscilloscope Calibrator 555 (CB19024E)
We found this circuit in a Texas Instruments application manual. The circuit provides a...