One-transistor oscillator (CB22064E)

Capacitors C2, C3 and C4 determine the frequency of this simple oscillator. Transistor can be general purpose equivalent.

Digital Speedometer (CB17306E)
This circuit, found in a 1986 documentation, uses an optical sensor to count pulses and, in its...
Automatic Answering (CB16250E)
This circuit, found in a 1997 publication, activates a lamp or a monitoring camera when the bell...
Electronic Cricket (CB12319E)
We found this circuit in an English publication in 1981. It can be improved by exchanging T1 for a...