| 摘要 |
PURPOSE:To prevent transmission efficiency from lowering, or to prevent deterioration in sound quality, by providing a re-modulation circuit which performs the FSK (Frequency shifted Keying) modulation of a data signal demodulated at a reception side, an providing a subtraction circuit which performs a subtraction process between a remodulation signal and a hybrid signal of data and sound. CONSTITUTION:A controller 1, in a communication time, sends the data signal from inputs, etc., from various kinds of I/O ports 5, to an FSK modulation circuit 6. Next, the data signal FSK-modulated at the FSK modulation circuit 6 is overlapped on a sound signal from a telephone set 8 at an adder circuit 7, and the hybrid signal of both signals is sent out to a telephone line l1. At a reception side, the hybrid signal is branched to two, and one is demodulated to a digital data at an FSK modulation circuit 9, then being branched to two, and one is received by the controller 1, and the other is modulated again with an FSK modulation circuit 10, then being sent to a subtraction circuit 11. A re-modulated data signal is subtracted from the hybrid signal in which the data signal is overlapped on the sound signal, and only the sound signal is taken out. The sound signal is sent to the telephone set 8.
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