Found in an English documentation, this circuit serves as a receiver for modulated sources of ultrasound. The sensor is a ceramic capsule. Transistors are general purpose types.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...