Crystal variable oscillator (CB9506E)

Found in Radio Electronics from the 90s, this circuit can vary the frequency in small values around the crystal frequency.

Model railway alarm (CB22528E)
This circuit detects traffic problems on a miniature railway by triggering an alarm. The circuit was...
Soft Start Regulator (CB15498E)
When establishing the voltage at the input of this regulator, the output voltage rises smoothly until...
JFET Audio Compressor (CB19998E)
This circuit was found in a Motorola documentation from 1975. Modern equivalent transistors such...