Signal generator (CB21057E)

Found in Popular Electronics, this '90s circuit generates harmonic-rich signals for testing audio equipment.

1 kHz Transistor Oscillator 1 (CB12906E)
This oscillator generates a 1 kHz signal, using an old germanium PNP transistor. The circuit was...
Answering Machine (CB18202E)
This 1985 circuit takes advantage of an old cassette recorder to answer and record phone calls,...
3A Regulator from 0 to 30 V LM350 (CB17197E)
This version of the circuit is from 2000, using a source of negative voltage that allows to obtain...