This buzzer trigger can be used for small alarms. We find it in an 80’s American documentation. The supply can be done with voltages from 3 to 18 V.
We found this circuit in an American publication from the 1990s. The circuit has a Darlington...
The sensor for this alarm is an LDR and it consists of an oscillator that goes into action when...
This circuit was found in a computer publication from the 1970s. The transistors can be the BD135...