| 摘要 |
PROBLEM TO BE SOLVED: To provide a telephone device which smoothly shifts to three way calling without depending on functions of a telephone network even during a telephone call between two persons. SOLUTION: A VoIP telephone device 1 simultaneously uses two telephone lines by a digital ADSL line 2a and one telephone line by an analog PSTN line 2b via a subscriber's line 2. When a telephone call to a third person is made or a call arrival from a third person is received while the telephone call is made between two persons, the telephone call with the third person is established by suspending the call with the present partner. The partner with the telephone call is changed by pressing down a catch button etc. When a party call button is depressed, the three way calling is started. The three way calling is established by performing a mixing process of sound signals by a switching circuit 13 and by delivering the sound signals between callers. COPYRIGHT: (C)2004,JPO&NCIPI
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