| 摘要 |
The communication between a supervisory controller and remote sites forming a group is executed using one pair of communication line and one modem. The circuit includes a communication controller (11) for controlling communication between a supervisory controller and remote sites, a MODEMs (12A-12D) for modulating incoming and outgoing data, an analog signal multiplexer (13) for multiplexing incoming and outgoing analog signal, a second modem (14) for modulating data incoming and outgoing from the analog signal multiplexer, and a remote site selector (15) for transmitting data (RxD) to a first - a fourth site (16A-16D), for transmitting transmission request signal of the sites to the modem (14), and for transmitting acknowledge signal of the supervisory controller to a corresponding site.
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