| 摘要 |
PROBLEM TO BE SOLVED: To utilize the additional service function of an ISDN network which is contracted with a certain line number by another line number by which the additional service is not contracted. SOLUTION: An ISDN terminal RTA 10 connected to a line with an additional service contract is called from TELA without the additional service contract. The RTA 10 calls TELA by using a free B channel and a state between TELA and TELB is made to be a speech state. When calling is received from TELC in this state, the RTA 10 transmits an incoming call from TELC to TELA. When call waiting is requested from TELA, the RTA 10 requests call waiting to the ISDN network 26, holds a call between TELA and TELB and the call between TELA and TELC is made to be a speech state. Then the RTA 10 outputs the changeover request and the transfer request of a holding call and a speech call to the ISDN network 26 and the applicable state is realized.
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