The Siemens EWSD periphery is comprised of the following:

• Remote Switching Unit (RSU) – Connects subscribers and trunks; can replace local exchanges
• Line Trunk Group (LTG) – Connects subscribers and trunks. These are some different types of LTG’s:
  • LTG(M): GSMYAA, GSMYDC, GPLSx, DIU120, PMUx, GPLC, etc.
  • LTG(N): GPNYx, GPNLx, etc.
  • LTG(P): GPPYx, GPSx, etc.

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Digital Line Unit (DLU) – Connects subscribers and concentrates the traffic to the LTG. These are some different types of DLU’s:

• DLU(A): SLMA:COS, SLMA:CMRL.
• DLU(B): SLMA:FPE, DLUS30, ALEX, SLMD:QFB.
• DLU(G): SLMA:ITM, SLMA:ITF, SLMD:QFB, SLMI:xxx, etc.

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The DLU can be re-used as an integral part of the Siemens NGN SURPASS access solution:

• Synchronous Transport Module Interface (STMI) – Provides a fully integrated STM-1 interface to the SDH network. It can be used to interconnect switches as well as to connect RSUs or RDLUs to the switch.
• Host Timeslot Interchange (HTI) – For connection of the RSU.