| 单词 | FDM (Frequency Division Multiplexing) |
| 释义 | FDM (Frequency Division Multiplexing) A multiplexing method by which multiple low speed incoming transmissions can share a single high speed outgoing analog circuit. An analog voice conversation requires bandwidth of 4 kHz. A voice grade analog local loop, therefore, provides an analog channel of 0–4,000 Hz. Such a loop is a two-wire circuit, comprising two physical conductors in a pair configuration. It is possible to equip a four-wire circuit to support multiple 4 kHz channels. In order to do so, a FDM multiplexer, or mux, must be placed on each end of the circuit.The muxes subdivide the bandwidth of the circuit into 4 kHz channels, each of which can support a voice grade transmission. So, an FDM mux might multiplex 24 voice grade channels of 4 kHz onto a four-wire circuit with total bandwidth of 96 kHz. All 24 channels coexist on the same physical circuit, separated only by frequency, as illustrated in Figure F-2. Within each channel, the voice conversation occupies the 300–3,300 Hz band and signaling and control functions take place over the 3,300–3,700 Hz band.The 0–300 Hz and 3,700–4,000 Hz bands are guard bands that provide channel separation in order to minimize the likelihood of mutual interference should the frequency channels overlap due to equipment malfunction or electromagnetic interference (EMI) from and external source. |
| 随便看 |
|
科学参考收录了5291条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。