Source : Free On-Line Dictionary of Computing

multiplexing
     
        1.  (Or "multiple access") Combining several
        signals for transmission on some shared medium (e.g. a
        telephone wire).  The signals are combined at the transmitter
        by a multiplexor (a "mux") and split up at the receiver by a
        demultiplexor.  The communications channel may be shared
        between the independent signals in one of several different
        ways: {time division multiplexing}, {frequency division
        multiplexing}, or {code division multiplexing}.
     
        If the inputs take turns to use the output channel ({time
        division multiplexing}) then the output {bandwidth} need be no
        greater than the maximum bandwidth of any input.
     
        If many inputs may be active simultaneously then the output
        bandwidth must be at least as great as the total bandwidth of
        all simultaneously active inputs.  In this case the
        multiplexor is also known as a {concentrator}.
     
        (1995-03-02)
     
        2.  Writing multiple {logical} copies of {data}
        {files}.  Placing the copies on totally separate {paths} to
        {mirror}ed {devices} greatly reduces the probability of all
        copies being corrupt.  Multiplexing differs from mirroring in
        that mirroring takes one data file and copies it to many
        devices, thus making it possible to copy a corrupt file many
        times.  Multiplexing writes the data files to many places
        simultaneously; there is no "original" data file.
     
        (2001-05-10)