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.
Passaje Alarm This locking circuit was found in a 1988 publication. It locks a relay when the...
Found in a publication for radio amateurs from the 1980s, this circuit amplifies signals in the 60...
We found this circuit in an application note from Linear Technology of the 90s. The circuit uses...