This circuit was obtained from Linear Technology documentation from the 80's. Powered by 5 V it can be used as a shield. The components are from the era.
The circuit shown here produces a pure square tone of 440 Hz that is suitable for musical...
This circuit was found in a 73 magazine for radio amateurs from the 90s. The circuit uses high...
This circuit is from a publication from the 70s, but it can be assembled with any diac and a Triac...