Operated directly from the power grid, this detector was found in an 80's RCA documentation. The sensor is an ionization chamber. The SCR triggers a warning siren.
This useful power supply was found in an 1985 Italian publication, but can still be assembled...
This headphone amplifier has good gain and high input impedance. The circuit is from Electronics Now and...
This CMOS integrated alarm was found in the July 1992 Radio Electronics magazine. The circuit has...