| 摘要 |
PROBLEM TO BE SOLVED: To discriminate whether the B channel of an ISDN line is under use or not in a simple configuration. SOLUTION: A serial/parallel converter 2 converts B channel data from an ISDN toward terminal equipment to 8-bit parallel data and outputs them to a latch circuit 3. A comparator 4 compares the octet data latched by the latch circuit 3 with the preset idle pattern. When both the data and the pattern are not coincident, a non-coincidence signal is outputted to a pulse generator 5. When the idle pattern continuously appears on the B channel, a significant signal is outputted from a timer circuit 6. Therefore, when the significant signal is outputted from the timer circuit 6, the non-use state of the N channel can be judged.
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