Process of transmitting multiple (but separate) signals simultaneously over a single channel or line.Because the signals are sent in one complex transmission, the receiving end has to separate the individual signals. The two main types of multiplexing methods are time-division multiplexing (TDM) and frequency-division multiplexing (FDM). In TDM (typically used for digital signals) a device is given a specific time slot during which it can use the channel. In FDM (typically used for analog signals) the channel is subdivided into subchannels, each with a different frequency width that is assigned to a specific signal. Optical-fibre networks can use DWDM (dense wavelength-division multiplexing), in which different data signals are sent in different wavelengths of light in the fibre-optic medium.
* * *simultaneous electronic transmission of two or more messages in one or both directions over a single transmission path, with signals separated in time or frequency. In time-division multiplexing, different time intervals are employed for different signals. Two or more different signals may be transmitted in time sequence: the instantaneous amplitude of each signal is sampled and transmitted in sequence. When all signals have been sampled, the process is repeated. The sampling process is carried out rapidly enough to avoid loss of essential information in the signal.In frequency-division multiplexing, each message is identified with a separate subcarrier frequency; all of these subcarriers are then combined to modulate the carrier frequency. For wire transmission, the modulated subcarriers may be transmitted directly without the introduction of a carrier frequency.The subcarriers are separated at the receiver terminal by frequency selection and the original message signal recovered from the subcarrier.
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