This interesting 1924 triode tube receiver was found in a documentation by Gernsback. Observe supply voltages. Coils are for tuned wavebands.
This circuit synthesizes a sinusoidal signal from logic pulses that can be obtained from an...
With the light falling on the LDR, the relay closes its contacts by activating a warning system. The...
This circuit was found in old English documentation. It can be improved by using resistors of...