| 单词 | narrowband |
| 释义 | narrowband 1. Voice grade bandwidth. In analog transmission systems, a narrowband channel has nominal bandwidth of 4 kHz, which is the standard for analog voice. In digital systems, a narrowband channel is 64 kbps, which is the fundamental standard for PCM digitized voice. 2. A channel or circuit of less than voice grade bandwidth. 3. Narrowband also is used to describe some number of 64 kbps channels (N × 64 kbps), but less than a T1 or E-1.T1 is a North American standard for a transmission system comprising 24 64-kbps channels and with a total signaling rate of 1.544 Mbps. E-1 is a European standard for a transmission system comprising 30 64-kbps information-bearing channels and with a total signaling rate of 2.048 Mbps. Narrowband ISDN (N-ISDN), for example, comprises two information bearing channels of 64 kbps, plus a signaling and control channel of 16 kbps, for a total of 144 kbps. 4. A circuit or channel offering relatively little bandwidth. See also bandwidth, broadband, and wideband. |
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