Digital Transmission Hierarchies - AbsoluteAstronomy.com

In telecommunications, the two following distinct digital hierarchical structures exist:

Plesiochronous Digital Hierarchy (PDH)

Plesiochronous Digital Hierarchy

The Plesiochronous Digital Hierarchy is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems...

Synchronous Digital Hierarchy (SDH)

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