This circuit was found in documentation for radio amateurs of the 1980s. This is the so-called roger-beep, which is the beep that is transmitted when the talk-listen function is changed.
The illustrated circuit uses the AUIRS2301 S from International Recfifier (www.irf.com) and is...
This timer was found in English documentation from the 80's. The integrated circuit is common...
This circuit is from an Electronic Design of the 90's. The circuit can be implemented with more...