RTTY Demodulator (CB21760E)

This circuit was found in a 1977 radio amateur manual. Integrated circuits are operational amplifiers of the time.

Anti Sleep Alarm (CB18464E)
This circuit is from a 1998 Poptronics. The circuit triggers a buzzer after a certain time, waking...
Voltage Indicator (CB16366E)
An integrated circuit 741 (operational amplifier is the basis of this voltage indicator, which can also...
Voltage Converter (CB22525E)
This transistorized voltage converter is one of the oldest that we find in technical publications. It...