| 摘要 |
PURPOSE:To simplify the constitution of a monitoring center and to reduce the burden of an operator, by providing plural sets of MODEMs corresponding to the modulating/ demodulating system of the MODEM of each terminal equipment at the monitoring center and selecting one whose modulating/demodulating system coincides with that of one terminal equipment with which messages are exchanged by means of a selecting means. CONSTITUTION:When data are transmitted to a monitoring center 1' from a terminal equipment 3, the data are transmitted to the center 1' by means of one circuit through the exchange of a data communication circuit. At the center 1', the data are inputted to each MODEM 7 and 11 and, after discriminating the MODEM 7 which makes an output, the MODEM 7 is selected by means of a selecting means 17 and the transmitted data are received through the selected MODEM 7. When data are transmitted from the center 1' to a prescribed terminal equipment 3, on the other hand, the MO DEM 7 of the monitoring center 1' is selected by means of the means 17, since the modulating/demodulating system of the MODEM of the terminal equipment 3 is already known and the MODEM 7 corresponds to the system, and the data to be transmitted are transmitted through the MODEM 7 after modulation. Therefore, the constitution of the monitoring center can be simplified without unifying the modulating/ demodulating system. |
