Plesiochronous Digital Hierarchy

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Plesiochronous Digital Hierarchy

(PDH) A transmission system for voice communication using plesiochronous synchronisation.

PDH is the conventional multiplexing technology for network transmission systems. The transmitter adds dummy information bits to allow multiple channels to be bit interleaved. The receiver discards these bits once the signals have been demultiplexed.

PDH combines multiple 2 Mb/s (E1) channels in Europe and 1.544 Mb/s (DS1) channels in the US and Japan.

PDH is being replaced by SONET and other SDH (Synchronous Digital Hierarchy) schemes.
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References in periodicals archive ?
PDH Plesiochronous Digital Hierarchy Two or more signals not generated from the same timing reference but nominally at the same frequency.
It will also provide radio delay technology for wide area transport, based on the Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) standards.