This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
This circuit works only with carbon microphones, due its low impedance. The speaker should be good or...
This circuit produces a sinusoidal signal whose frequency can be calculated using the formula next...
This circuit was found in the 1987 Radio Electronics magazine. The components used are integrated...