PC address decoder (CB20536E)

This TTL decoder circuit for PC ports was found in a document from 1992. The power supply can be PC's own circuit.

Code Practice Oscillator (CB4165E)
This unijunction transistor oscillator is intended for Morse code practice. The circuit is from an...
Crystal Overtone Oscillator (CB5112E)
The capacitors of this 80's circuit must be ceramic and the transistor can be any PNP that...
Beat Oscillator (CB4208E)
Placed near a common receiver, this oscillator is intended to generate a beating signal to receive...