This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
We found this circuit in an old documentation. The integrated circuits used are specific to...
The integrated circuit used in this application is uncommon today and specific to the application, as it...
This 3-transistor buzzer or buzzer is a classic type found in the July 1998 issue of Electronics Now...