Constant current source (CB20484E)

This circuit uses a current regulator from the 90's. This component is uncommon nowadays. The transistor admits equivalent.

Reflex receiver (CB20557E)
This 1-transistor reflex receiver was found in a 1963 publication. The coil is for the mid wave...
Unijunction Oscillator (CB928E)
This is the normal circuit of a relaxation oscillator using an unijunction transistor such as the...
Variable Sound Effect (CB15048E)
This circuit produces a whistle sound when acting on switch S1. Aids is applied to a transformer that is...