| 单词 | V.90 |
| 释义 | V.90 The ITU-T Recommendation (1999) for full-duplex (FDX) asynchronous dial-up modems oper- ating over the public switched telephone network (PSTN) at transmission rates up to 56 kbps downstream and 33.6 kbps upstream over a 4-kHz analog voice grade channel. In order to achieve this level of performance, a 56 kbps modem configuration requires that only one transmission link be analog.The end user dial-up connection is through a V.90 modem over an analog local loop to the PSTN. The connection through the PSTN must be entirely digital, including the originating and terminating central offices (COs), all tandem offices, and all transmission facilities.The local loop connection at the corporate intranet site, Internet service provider (ISP), or other site also must be digital, such as T-carrier, E-carrier or ISDN. 74570c22.qxd 9/12/07 12:48 AM Page 518 |
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