We found this circuit in a 1991 Hobbyst Electronics. The circuit makes use of an unusual transducer today. It is a piezoelectric buzzer that can eventually be replaced by an equivalent configuration.
The circuit shown in the figure was found in a 1974 publication. The field effect transistor may...
I found this circuit in an English publication from 1989. This configuration can be mounted with...
We found this circuit in a small espionage manual from 1993. The components are current, and the...