We found this circuit in the July 1992 issue of Radio Electronics magazine. An optical system produces the light beam that, when interrupted, triggers the alarm. The sensitivity is adjusted by R4.
Found in a 1968 American documentation, this circuit generates 1 kHz signals. The SCR used is not a...
This circuit with bass and treble control and 10 W of power per channel is from the SGS manual of...
More modern operational amplifiers can be used on this instrument to measure alternating voltages. The...