| 摘要 |
Disclosed is a communication terminal apparatus for use in a communication system in which at least one line having a plurality of channels is used by a plurality of communication apparatuses (4, 5, 6, 7, 8, 9, 10), wherein when all the information channels are engaged, the idle condition thereof is automatically monitored, and a call is originated when the idle condition is detected, thereby eliminating the wastefulness of operation and improving the efficiency of the line. In particular, when the communication terminal apparatus is connected to a subscriber's line (3) of an ISDN system, communication is effected by using B channels, and if all the B channels are found to be busy upon origination of a call, the idle condition of one of the B channels is monitored from the contents of a D channel, a call being originated again when a B channel becomes idle.
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