| 摘要 |
PURPOSE:To prevent a noise by bringing an encoder output bit to a bit inversion at every sample period and outputting it to a trasmission line, and also bringing a bit inversion output which is obtained through its trasmission line, to a bit inversion and outputting it to a decoder. CONSTITUTION:An input code train of an encoder 1 is inverted by a bit inverter 9. Subsequently, its code train is outputted to a transmission line X through a switch 4. Next, it is inverted by a bit inverter 12 through a switch 5 of a receiving side, reproduced to a sound signal by a decoder 6, and sent out to a terminal D. In case the circuit is disconnected, the code train on the transmission line all becomes the same code in which '1' or '0' is consecutive, but by the respective bit inverters 1 (13,14) of the side of the decoders 6 (7,8), the input code train to its decoder 6 becomes 01010-, and becomes a DC waveform whose amplitude is constant. When an integrator of the encoder 1 and the decoder 6 is a leakage type, the DC component is attenuated as the time elapses, and before the rotational connection, an output of the decoder 6 becomes a non-signal state, and it does not occur that a noise offensive to the ear is transmitted to a receiving person of a terminal immediately after the rotational connection.
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