Home - Products - Telecommunication equipment - Plesiochronous multiplexers

Plesiochronous multiplexers

Plesiochronous Digital Hierarchy (PDH) is a digital technology for data and voice communication based on time-division multiplexing (TDM) and pulse-code modulation (PCM) for representation of a signal.

PDH technology uses a 64 kbit/s input signal of digital signal level (DS0) to generate output data stream at a bit rate of n×64 kbit/s. The DS0 group carrying payload involves stuff bit groups necessary for synchronization and phasing, signaling, cyclic redundancy check (CRC) for the group to obtain a cyclic form.  

The ITU-T Recommendations specify several PDH levels: 

  • Level 1 – 2048 kbit/s bit rate (E1);
  • Level 2 – 8448 kbit/s bit rate (E2);
  • Level 3 – 34368 kbit/s bit rate (E3);
  • Level 4 – 139264 kbit/s bit rate (E4).

    ИКМ-30 is a base data rate for making higher PDH levels. Channelizing of higher PDH levels takes place as follows: 4 E1 tributaries are multiplexed in a single E2 tributary, 4 E2 tributaries are multiplexed in a single E3 tributary, 4 E3 tributaries are multiplexed in a single E4 tributary. The multiplexing process includes bit stuffing to bring bit rates to a common rate by inserting stuff bits.


    PDH multiplexers are designed for multiplexing/demultiplexing of digital channels according to the hierarchy level used in the multiplexer.

    		•