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.
In this circuit, suggested by the Motorola Linear Databook of 1990, the resistors depend on the...
This circuit is used for cable checking. We found it in the Radio Electronics magazine of December...
We found this circuit in a 1965 Electronic Design. Transistors are still common but admit...