This circuit is quite simple to assemble, having been found in a traditional American publication. The transistor can be a BC548 and the power can also be done with a voltage of 6 V from source or battery. The wires for the 8-ohm speakers, which also function as microphones, must be a maximum of 15 meters. Switch S2 acts as a talk-listen switch and S1 turns the power on and off. It is an ideal circuit to be used as an electronic door-phone. The 200uF capacitor can be replaced with the commercial value 220uF.
