| 摘要 |
The communication terminal of the present invention receives ISDN information of ISDN containing information channel data of an information channel (B-channel) and control channel data of a control channel (D-channel) from an ISDN network. The communication terminal comprises an extracting circuit and a comparator circuit continuously extracts the information channel data in synchronization with the reference pulse, and compares at least two continuous extracted information channel data. The determination circuit determines that there is a change in at least two continuous information channel data based on the result of comparison in the comparator circuit, and generates a determination signal indicating that the information channel is in busy or not. To detect usage by data of data communication series, in addition to the above circuits, includes an identification circuit for identifying idle data in an idle state in said information channel data, difference determination circuit for determining difference between the information channel data extracted and the idle data, and a usage determination circuit for outputting a determination signal indicative of usage of said information channel responsive to a determination of said difference determination circuit.
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