| 摘要 |
PROBLEM TO BE SOLVED: To prevent useless dial operations by broadcasting the presence or absence of the plural idle information channels via a control channel of an outgoing channel and selecting at random plural control channels to access them via a terminal when an idle information channel is available. SOLUTION: A center device is constituted of a switchboard 11, an interface device 12, a time division multiplex access device 13, etc. Then every terminal connected to a transmission line performs the two-way communication, via a center device by making use of the time division multiplex channels of communication bands which are separated in each frequency bands of both incoming/ outgoing-transmission bands. Each of incoming/outgoing-channels consists of plural information and control channels, and the control channel of the outgoing- channel led from the center device broadcasts the presence or absence of the plural idle information channels. Then a terminal selects at random plural control channels and accesses them, when an idle information channel is available. |
