> For the complete documentation index, see [llms.txt](https://tmediadocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://tmediadocs.telcobridges.com/products/tmedia/features-and-solutions/features/redundancy-and-high-availability/hardware-tdm-interfaces.md).

# Hardware:Tdm Interfaces

TelcoBridges products supports 3 types of [line interfaces](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/line-interface) in 4 possible [TDM modules](/products/tmedia/installation/tdm-module-options.md).

### Redundancy

#### SONET/SDH

Only the [SONET/SDH interfaces](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/sonet-sdh-interfaces) have an innate redundancy feature. There are 2 ports per [SONET/SDH interfaces](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/sonet-sdh-interfaces) modules: Main and APS (Automatic Protection Switching). In the eventuality where the Main fiber is damage or disconnected, the APS can take over and resume service.

#### Line Service Distribution

The DS3 and E1/J1/T1 interfaces doesn't have redundancy connectors. To minimize the effect of a [line interface](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/line-interface) failure, it is recommended to distribute groups of [line services](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/line-service) of each devices between providers when possible. This create share loading between devices and avoid overwhelming a system provider because all the traffic are redirected to a single device.

**Recommended Setup**

This is a recommended setup when using DS3, SCSI or RJ48 interfaces:

![Line Service Ha Distribution](https://docs.telcobridges.com/w/images/9/92/Line_Service_Ha_Distribution.png)


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