This circuit makes use of a specific 80's component and was found in an American manual of the time. A matrix keyboard allows you to select one of several music programs.
This circuit was found in an English publication from the 80's. It triggers a buzzer (with...
This is an amplifier stage with a typical germanium transistor from the 60's to the 70's. The...
This circuit was found in a Motorola Manual of 1965. The circuit has neon lamps as trigger...