Found in a 1990s US publication, this alarm circuit detects when a light beam is interrupted. Optical resources may be used for the sensor and instead of the alarm a relay may be used.
This circuit was taken from the 1974 Ferranti transistor manual. Note the shapes of the signals....
This mini siren, found in a 2003 publication, powers a small piezoelectric transducer, but a...
This fuzz effect is from a 1988 Italian publication, but it can be easily assembled, as the...