Data transmission system for transmitting information from a central control unit to a plurality of terminals

摘要

A data transmission system includes a polling modem and a central control unit that receives a response signal from a terminal. A data transmission central control unit performs polling type transmission to transmit an information data unit to the terminal that has requested the information data unit. The central control unit also performs loop type transmission to cyclically transmit information data units with their loop flags being set to the terminals in succession. The control portion in the terminals selects the transmission that requires the shortest waiting time.