This 1924 receiver uses a battery for the tube filaments and a high voltage battery for the amplifier and detector circuit. The speaker is kind of high impedance era.
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...