Optical shield (CB20698E)

This circuit was found in American documentation from the 90s. The coupler is the type that uses a photo-Darlington.

Variable Sound Effect (CB15048E)
This circuit produces a whistle sound when acting on switch S1. Aids is applied to a transformer that is...
Regulated power supply (CB23737E)
This power supply circuit, slightly different from the conventional one, was found in the Radio...
Guitar Sustain Unit (CB14949E)
This guitar effect pedal was found in 1982 documentation. The circuit can be easily assembled with...