Found in a 1980s documentation, this circuit uses transistors from that time. Modern equivalents can be used. The alarm is a piezoelectric buzzer with na included oscillator.
This high-performance circuit was found in the 1982 SGS Linear Integrated Circuits Manual. The...
This circuit for audio applications was found in an English magazine from the 80's. The circuit...
The circuit presented uses an integrated circuit Sanyo, not very common in our day. This amplifier provides...