| 摘要 |
PURPOSE:To realize a conference telephone system made possible for conversation by connecting three or more terminals at the same time, in a telephone network taking vocoders using linear forecast coding as terminals for encryption of speech. CONSTITUTION:N+1 sets of vocoders 1-0-1-N, are installed corresponding to N+1 sets of calling devices, and a vocoder 2 is connected to a vocoder 1 by a manual or automatic exchanger. A controller 7 discriminates the presence of call and preceding or succeeding through a control signal 8-i and makes a control so that the received reception analog signal 6-i is one of transmitted analog signals 5-i at all times. If a caller of the No.0 is selected, a transmission call switcher 9-0 is closed and a transmission analog signal 5-0 only is amplified at an amplifier 12 and transmitted to N sets vocoders 2 and gives the reception call analog signal 6-i to speakers other than the No.0. To the No.0 caller, it is informed as an audio signal from a signal source 13 via a switcher 11-0 and the vocoder 1-0. |
