We found this circuit in a French documentation from the 80's. The components used are still common and the circuit can generate signals from 10 Hz to 100 kHz.
In the figure we have the way to adjust the output null of an operational. The configuration...
This simple circuit uses an SCR to lock the alarm once triggered. The circuit is from an English...
We found this circuit in the March 1992 Radio Electronics magazine. The circuit provides 100 Hz...