AC voltage control (CB8904E)

This circuit was found in a 90s Hands On Electronics. The semiconductor component is a Triac of the time.

Refrigerator Alar (CB1351E )
Placed inside the refrigerator, this circuit triggers an oscillator when the part is opened...
Voltage Controlled Oscillator (CB14355E)
This circuit was found in the Linear Applications Handbook of the National Semiconductor of 1994....
Inductive switch with the TCA106 (CB21893E)
This circuit was taken from the 1976 Siemens Integrated Circuits Manual. The TCA106 is an...