This circuit was published in the July 1993 issue of Electronics Now magazine. It uses a sensor from the time and triggers a buzzer with a Sonalert-type oscillator.
Using an operational amplifier of the time, this circuit was obtained from a 90s Radio...
Equivalent transistors like the BC548 can be used on this 1969 Mullard circuit. The circuit has two...
This circuit is from 1995 documentation. The power depends on the transformer, which in this case...