This interesting 1924 triode tube receiver was found in a documentation by Gernsback. Observe supply voltages. Coils are for tuned wavebands.
This circuit, with the help of a 15 V x 1 A source, allows to measure small resistances,...
This circuit uses a piezoelectric transducer to produce sounds like a buzzer. Frequency is...
We found this circuit in a Texas Instruments optoelectronics manual. The audio modulator serves for...