This circuit generates the busy tone of ordinary telephones. The transistors can be the BC548 and the components of the T filter and the multivibrator can be changed to obtain the exact tone.
This circuit is suitable for incandescent lamps but can be adapted to work with LEDs. The circuit is...
We find this circuit in the 80's own component manual itself. The characteristics of the circuit...
This source, obtained in the 1982 SGS manual, has pre-regulation and provides a current according to...