| 摘要 |
PURPOSE:To connect a handset comprising a carbon type transmitter and an electromagnetic receiver to a telephone set equipped with a handset other than the carbon type transmitter and the electromagnetic receiver by providing a current supply function and an impedance conversion function. CONSTITUTION:Resistors R3, R4 constitute the current supply section to the carbon type transmitter 2 and the operating current of the carbon transmitter 2 is supplied by voltage +V. Further, resistors R1, R2 and a capacitor C1 constitute a level conversion section 7, by which the output level of the carbon transmitter 2 is converted so as to be suited to the telephone set main body 1 by selecting the resistors R1, R2 and the capacitor C1. Then transistors Q1, Q2 are of NPN and PNP types, they are operated in a complementary way to drive the electromagnetic receiver 3 via a capacitor C3.
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