This LM380-based circuit was found in documentation from the 1980s. The components are current, and the transistor may be a general-purpose equivalent. Note the use of a medium impedance speaker.
This bistable touch circuit using CMOS technology controls a relay. The supply voltage must be...
This project is from the book Science Fair Projects by Newton C. Braga. In it we have a relay that...
This circuit was obtained in an old documentation, but it is still current by the used components....