| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching system which uses an idle line to originate a call in the case that the idle line exists in a channel group to which a trunk group belongs though a maximum number of lines set in this trunk group are all busy. SOLUTION: In the switching system which can use a call by call function in ISDN, a control circuit 31 detects whether input to release the set call by call function has been performed or not and discriminates whether the maximum number of lines preliminarily set for the trunk group which originate a call are all busy or not. If the maximum number of lines are al busy, the control circuit 31 validates the input to release the call by call function and discriminates whether or not an idle line exists in another trunk group in the channel group to which this trunk group belongs, and the control circuit 31 uses the idle line to perform call originating processing when existence of the idle line in another trunk group is detected.
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