Digital multiplex hierarchy

In telecommunication, a digital multiplex hierarchy is a hierarchy consisting of an ordered repetition of tandem[?] digital multiplexers that produce signals of successively higher data rates at each level of the hierarchy.

Note 1: Digital multiplexing hierarchies may be implemented in many different configurations depending on (a) the number of channels desired, (b) the signaling system to be used, and (c) the bit rate[?] allowed by the communications media.

Note 2: Some currently available digital multiplexers have been designated as Dl-, DS-, or M-series, all of which operate at T-carrier rates.

Note 3: In the design of digital multiplex hierarchies, care must be exercised to ensure interoperability of the multiplexers used in the hierarchy.

Source: from Federal Standard 1037C and from MIL-STD-188