Voltage amplifier with the 37 tube (T392E)

Found in a modern design book with tubes, this stage with the triode 37 has a plate current of 3.7 mA.

Recording tapes eraser oscillator (CB7303E)
This 70 kHz oscillator is used to erase tapes in pre-recording. The circuit is from 1968 General...
Automatic Frequency Control (CB4101E)
We found this circuit in an old documentation for hams. In it we have the way to use a varicap to...
Touch or Proximity Alarm (CB17329E)
This sensitive touch circuit that triggers an oscillator uses only transistors. The circuit is...