| 摘要 |
PURPOSE:To make the provision of accurate oscillators unnecessary at each station and to avoid the distortion of communication due to shift in modulation/demodulation frequency, by obtaining the carrier wave of each station with the reference frequency transmitted from a master station. CONSTITUTION:A reference frequency P1 produced at a master station A is transmitted to a transmission line L2 and a reference frequency P2 generated at a master station D is transmitted to a transmission line L1. At each station, the reference frequencies P1 and P2 are inputted to a switching section 40, which monitors the input level of the reference frequency P1. If it is more than a fixed value, this is selected and outputted and fed to a carrier wave generating section 30. The section 30 multiplies the reference frequency P1 to produce each carrier wave to be fed to a frequency conversion section 50. The section 50 modulates an input channel signal S0 and transmits a line signal to transmission lines, and demodulates the line signal inputted from the transmission line to demodulate channel signal S0. Thus, the channels with arbitrary stations can be constituted by using arbitrary channel. Slave stations B, C do not include a main oscillator 1 and a frequency dividing synthesizer 20. |
