| 摘要 |
In the present invention, a plurality of terminal devices 3 are connected to a parent device 1, and the analog voltage of the terminals is measured. A reference voltage 6 and a measurement voltage 7 are successively switched and connected at a voltage having the reverse polarity of clocks supplied by the parent device 1, in the intervals between the clocks. The reference voltage 6 and the measurement voltage 7 of a terminal device 3 are thereby directly connected. With this mechanism, a multi-point analog measurement signal can be measured with one pair of electric wires. Errors due to a voltage drop brought about by the transmission channel 2 of the measurement voltage 7 are corrected by measuring the reference voltage 6 known in advance, and a correct analog measurement is possible. Also, by turning the fixed measurement voltage 7 and reference voltage 6 on and off with a terminal-device-side connection signal, analog signals and connection-point or integrated-value digital signals can be mixed and transmitted. A device is thus achieved with which it is possible to transmit a plurality of correct analog signals and digital signals by time division, using the one pair of electric wires. |
