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 circuit was obtained in Linear Technology documentation from 1993. The circuit provides 3.3 V and...
This circuit is from the National Semiconductor CMOS manual of 1977. What this circuit does is to...
This circuit operates from 25 to 65 kHz depending on the transducer used and the settings. We...