| 摘要 |
PROBLEM TO BE SOLVED: To provide the polling system that can build up a transmission system at a low cost where a size of slave stations is made small, installation cost of a master station and the slave stations is reduced and a temperature environment of the installed location is less limited. SOLUTION: A transmission section 10 of a master station A has an oscillator 2 that oscillates a call signal being a continuous sine wave signal with frequencies different from slave stations B and a distributor 3 that distributes the call signal oscillated from the oscillator 2 to an outgoing transmission line L1 and a local transmission line L3. A reception section 30 of the slave stations B has a filter 4 that receives the call signal and passes only the call signal with a frequency assigned to its own slave station B. A transmission section 40 of each slave station B has a mixer 6 that applies frequency conversion to a slave station data signal based on the call signal passing through the filter 4. A reception section 20 of the master station A has a mixer 8 that applies frequency conversion to the signal received via an incoming transmission line L2 by using the signal received via the local transmission line L3 and a demodulator 9 that demodulates the frequency-converted signal into the slave station data signal. |
