This sensitive motion sensor with inductive sensor was found in a 90s Elektor. The circuit uses only transistors to activate a buzzer.
This circuit, very critical due to the frequency at which it operates, was found in an American...
Found in 90’s English documentation, this rising and falling siren, manually activated, drives a...
This circuit, found in a 1958 magazine, is for reference only, since the components are not easy...