This circuit was found in a 90s Popular Electronics. It generates tones given by the oscillators and can be changed. The circuit already includes an amplification stage.
This circuit, from a documentation of the 90s, uses unusual operations today, but the...
This circuit is from a Radio Electronics from May 1994. In it we have the way to connect three 4017...
This circuit is from the 70's by A. Fanzeres. We kept the original text. It has already been said...