In use telephone indicator (CB8657E)

Found in a 90s Popular Electronics, this circuit keeps an LED on when a phone is in use. Can be used with extensions.

Infrared detector (CB7108E)
This circuit was found in a Philips documentation from 1967. The circuit uses components from the...
Simple NiCad charger (CB9532E)
Found in old documentation, this circuit consists of a simple power source where the transistor must be...
Corona wind generator (CB9439E)
An electric wind flow obtained by the corona effect can be obtained with this circuit from Radio...