| 摘要 |
PURPOSE:To make a signal type convertor circuit unnecessary by carrying out transmission by means of frequency multiplication without converting the output signal of a channel selector into a code. CONSTITUTION:In a channel selection signal processing part at the terminal side, an encoded pulse string outputted from a code generator circuit 13 is modulated into a carrier having absolutely the same frequency as that of channel selectors 81-8n by a modulation circuit 14, and transmitted. These signals are converted into totally different types of frequency by frequency convertor circuits 202-20n, and frequency-multiplied by a multiplier circuit 12. In a channel selection signal processing part at the center side, photoelectrically converted signals by transmitting optical fiber are separated at every frequency by type of each carrier in a separator circuit 18. After they are demodulated in a demodulator circuit and converted into an original pulse string, they are parallel-converted in a series/parallel convertor 191, and then branched into three segments. One signal out of three branched segments decides whether a signal outputted from a channel selector is that to control a video signal selection circuit, or that to control a video signal selection circuit in other remote video signal center, controls a switch 21' or a switch 21'', and turns the former on and the latter off.
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