| 摘要 |
PURPOSE:To simplify the circuit constitution of a receiver by inverting a data signal to be shifted to a carrier with a low frequency in two different carriers to allow a receiver to invert the demodulated data signal. CONSTITUTION:Since a data signal inputted to a modulator-demodulator 27 is shifted to a lower frequency carrier, subjected to control of a CPU25 and inverted by a data signal inverter 20 and inputted to the modulator-demodulator 27. then the carriers having two different frequencies subjected to FSK modulation by the modulator-demodulators 26, 27 are switched in time division by a carrier switch 28 controlled by the CPU25, mixed with a multi-channel television signal sent from a TV signal modulator 30 through a mixing distributor 29 and sent to plural subscriber terminal equipments (receivers). A data signal of a carrier FRF2 having a lower frequency in the two different carriers is inverted by a center equipment and a demodulated IF data signal fIP2 at the receiver side is processed as it is without being inverted and demodulated.
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