This small tube amplifier appeared in Radio Electronics magazine in February 1958. The circuit is powered by the mains with a power transformer and output with different impedances.
This circuit uses high voltage transistors to provide direct power from the 110 V power grid or a...
This circuit was designed to work with the previous one in triggering a relay by the sounds picked up...
This circuit was suggested by Signetics in 1980s documentation. The circuit makes use of the...