This circuit was found in 1980s American documentation. The transducer is a piezoelectric capsule and the power supply voltage can be between 3 and 18 V.
This circuit was found in Radio Electronics magazine from October 1966. It consists of a rhythmic...
This circuit is from a Popular Electronics from the 90's. The circuit provides an output for a...
The transformer of this unit found in an old Japanese documentation can have 22 to 25 V of...