Filament source (T398E)

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

Humidity Sensor (CB4912E)
This circuit was obtained from a Linear Technology manual from the 1990s. The components may have...
Multitester (CB3834E)
This simple multitester tests continuity, semiconductors, leaks, and other common component...
Emitter Triggered Flip Flop (CB994E)
This flip-flop using two bipolar transistor was found in a publication of the year 1968. The...