This circuit with the HA2400 was found in the March 1980 Radio Electronics magazine. The circuit has digital-gain control and must be powered by a symmetrical 15 V source.
This source, found in a 1991 publication, was originally designed to operate with the CB18736E, an alarm...
We found this circuit in a publication of 1990. With the changes it can be mounted easily today....
This circuit mimics the sound of a siren when we turn the axis of the small DC motor. The...