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Multiplexing. Multiplexing. Multiplexing. PDH. Multiplexing. Plesiochronous digital hierarchy (PDH) each TDM stream was derived using a separate timing source Justification bits Synchronous digital hierarchy (SDH) all equipment is synchronized to a single master clock
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Multiplexing • Plesiochronous digital hierarchy (PDH) • each TDM stream was derived using a separate timing source • Justification bits • Synchronous digital hierarchy (SDH) • all equipment is synchronized to a single master clock • Synchronous transport module level 1 or STM-1 is 155.52Mbps • A section is a single length of transmission cable • Section Termination equipment (STE) : repeater • A Line extends across multiple cable sections and is terminated by a line termination equipment (LTE) -> multiplexers and switching nodes • A path is an end-to-end transmission path through the complete transmission system • Each frame comprises 2430 bytes and repeats every 125 microsec. • A frame comprises nine 270-byte segments each of which has a 9-byte header associated with it and a 261-byte payload