Indicated for the protection of three-phase systems, this circuit was found in an American documentation of the 70's. The circuit can be implemented with modern components.
The circuit presented was obtained from a 1976 Italian Radio Elettronica but can be easily...
This crystal-controlled circuit with 60 mW output power is in the Radio Electronics magazine of...
This circuit is from a 1981 publication. The DC supply can be made with voltages from 6 to 12 V...