facsimile modulation的意思|示意

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Facsimile modulation，or FDM，is the process of modulating an analog signal to produce a modulated output signal. FDM is often used to transmit audio, video, and other information signals over telephone lines and other mediums.

FDM works by taking an analog signal, such as an audio signal or video signal, and converting it into a digital signal. The digital signal is then further divided into several sub-signals, which are each modulated onto a separate carrier frequency. The modulated signals are then sent over the medium, and the receiver demodulates them to reconstruct the original signal.

FDM is commonly used in radio and television broadcasting, whereby a single radio or television signal is split into multiple, smaller signals, each carrying part of the original signal. For example, a television broadcast may be split into several sub-signals, each carrying a different part of the audio and video signals.

FDM is also used for data transmission, such as for telephony, where voice signals are modulated onto a carrier frequency before being sent over telephone lines. FDM is also used in digital subscriber lines (DSL) and cable television, where the data is modulated and sent over coaxial cable.

FDM is useful for transmitting data over long distances and can also be used to reduce interference from other signals. Additionally, FDM allows for signals to be sent over multiple channels, thereby allowing for transmission of multiple signals in parallel. The main benefit of FDM is that it is relatively simple to implement, making it a cost-effective solution for data transmission.