Microammeter (T465E)

Found in a 1948 MIT documentation, this circuit uses a 0 to 100 uA microammeter as an indicator. The power supply is 150 V.

Decade Counter with Nixie Tube (CB20141E)
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
Crystal Radio (CB14015E)
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
Headphone amplifier (CB23888E)
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...