42 kHz oscillator (CB21805E)

This circuit was used as an eraser for old tape recorders. The circuit is from a 1960 Mullard transistor manual.

Headlight indicator 555 (CB9118E)
This circuit warns when the headlight bulb is on. We found it in a Popular Electronics from the...
Variable Active Cycle 4093 (CB15916E)
The oscillator shown in the figure keeps its frequency constant in an active cycle adjustment...
Two-Transistor MW Receiver (CB23975E)
This circuit was found in an Argentine publication from the 1970s. The circuit can be assembled with...