Filament source (T398E)

Despite being transistorized, this is a constant current source circuit for 1 V valve filaments such as the 1H4 tube.

Wireless AM Microphone (CB16392E)
This is the project found in a 1981 publication, but it is still viable. It is a simple AM...
3A Adjustable Regulator LM123 (CB14509E)
The LM123 series (223 and 333) is manufactured by several semiconductor companies. The circuit below...
Bistable with 2 SCRs (CB23947E)
This circuit is from a Radio Electronics magazine from June 1969. The circuit uses two SCRS to...