This circuit using the CK722 among others came out in a September 1950 Radio Electronics. It was one of the first circuits of this type published with transistors that started to reach the market.
This cricket circuit obtained in a 1992 documentation has an amplifying stage that, however, takes...
This circuit was found in a 1980s English publication, but can still be easily assembled by the...
This circuit is from old documentation, but can be adapted to use modern components. Power...