We found this circuit in an American 1980s documentation. The circuit uses a piezoelectric transducer unusual in our day. The transistor is general purpose type.
November 2016 - Already available from Mouser Electronics on Texas Instruments' new DS280BR820...
April 2017 - Littelfuse's new two-way discrete TVS diodes for protection against ESD up to 30 kV...
This protection circuit short-circuits a load when the voltage exceeds a certain value causing the...