| 摘要 |
PROBLEM TO BE SOLVED: To install the electronic bulletin board system very easily by providing a transmitter having a receiver receiving a signal sent as a radio wave from the bulletin device and a mixer mixing a community signal or the like to a wired path between a reception section and a terminal receiver. SOLUTION: A primary local oscillator 32 of a transmitter 30 oscillates a signal acquired by a receiver 31, that is, a video signal (frequency f1) from the bulletin device at a frequency F1. A BPF 33 of a next stage gives an output signal f22 of the primary local oscillator 32 to a secondary local oscillator 34, which oscillates a signal with a frequency F2. Then a frequency f31 (=F2 +f22 ) of two oscillated frequencies is fed to an LPF 35 of a next stage, only a signal at a low frequency band is outputted to a mixer 36 and the mixer 36 mixes a signal with a frequency f31 with a community signal. Then the frequency of the signal mixed by the mixer 36 is set optionally by changing the oscillated frequency of the bulletin device and primary and secondary local oscillation frequencies F1, F2 to assign a sharp video image on an optional idle channel. |
