Variable regulator with crowbar protection (CB21189E)

This circuit was found in a Popular Electronics from the 90's. The power transistors must be equipped with a heat sink.

Oscillator up to 50 MHz (CB23739E)
The frequency of this oscillator depends on the crystal used and the transistors. The circuit was...
MOSFET Stage (CB25576E)
This circuit shows how to use the 4007 MOSFETs in an amplifier stage. We found it in an...
Touch Sensor (CB18350E)
This circuit was found in a 1967 Japanese documentation. It consists of a touch control system with...