> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/protocols/sonet-sdh-interfaces.md).

# SONET/SDH interfaces

The [Tmedia](https://telcobridges.com/media-gateways/products/tmedia-gateways/) [TMG3200](https://telcobridges.com/media-gateways/products/tmedia-gateways/tmg3200/) and [TMG7800](https://telcobridges.com/media-gateways/products/tmedia-gateways/tmg7800/), as well as the [Tdev](https://telcobridges.com/products/development-platforms-tdev/) [TMP6400](https://telcobridges.com/products/development-platforms-tdev/tmp6400-tdev-voip-gateway-development-platform/), can accommodate an interface for up to two SONET or SDH lines: one for operating as the active link with the other link operating in standby mode for emergency switchover.

In the case of a SONET interface, an OC3 line interface is configured to serve a selection of line services. In the case of an SDH interface, an STM-1 Optical line interface with related line services are configured. A conceptual image is shown below:

![Sdh supported hierarchy](https://docs.telcobridges.com/w/images/5/5d/Sdh_supported_hierarchy.png)

![Sonet supported hierarchy](https://docs.telcobridges.com/w/images/e/ea/Sonet_supported_hierarchy.png)

Note: Combination of E1s and T1s within a DS3 is not supported.

* [Allocating OC3/STM-1 line interface](http://docs.telcobridges.com/mediawiki/index.php/Toolpack_v2.3:Creating_a_Primary_Line_SONET/SDH_Interface) Keywords: AU3, AU4, VC3, VC4, VC11, VC12, VT2, VT1.5, TU3, DS3, TU12


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