We found this circuit for video games in a Radio Electronics magazine from August 1977. The transistor can be any common RF type that reaches the desired signal frequency.
Using 4 operational amplifiers this circuit generates 4 different tones. The circuit is from an...
In the figure we have an application of an oscillator 4013 as voltage multiplier. It consists of a...
This Colpitts crystal oscillator was found in an American publication for amateurs in the 1980s....