This circuit, which can be seen elsewhere on this website, was obtained from a 90’s English documentation. The circuit drives a small speaker, but for greater volume an external amplifier must be used.
Found in a 90’s Radio Electronics, this circuit uses a component from the time, difficult to find today....
This circuit was found ina 90s Popular Electronics. It is intended for switching analog video...
We found this alarm circuit in a Radio Electronics magazine from July 1990. The power transistor must be...