Light test (CB8789E)

This light-sensing probe was found in a 90s Popular Electronics. The circuit detects light sources by triggering a buzzer.

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...