In carrier systems, many different forms of multiplexing may be used, such as time-division multiplexing and frequency-division multiplexing.
Multiple layers of multiplexing may ultimately be performed upon a given input signal; i.e., the output resulting from one stage of modulation may in turn be modulated.
At a given node, specified channels, groups, supergroups, etc. may be demultiplexed without demultiplexing the others.
Source: from Federal Standard 1037C and from MIL-STD-188