Relative impedance meter (CB7487E)

Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent transistor like the BC558.

3 V power supply (CB17037E)
This unit is intended to power 2 AA or AAA battery powered applications from the car battery,...
Schmitt Trigger (CB21849E)
We found this circuit in the 1974 Ferranti transistor manual. Transistors are from the time, being...
Optocoupler Code Practice (CB26321E)
This ingenious circuit was found in a 1990s Popular Electronics. The oscillator is a 555 and the...