This simple circuit for a high impedance magnetic phone (500 ohms or more) has been found in a Spanish documentation of 1983. The circuit can be powered by 1 to 4 small cells and the coil consists of 80 to 100 turns of enamelled wire 28 to 32 in a Ferrite rod. It is recommended to use a long antenna. The transistor may be the BC548.



N° of component