> 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/clocking.md).

# Clocking

The clock is a necessary component of a TDM network. Synchronizing your system with the right clock, allows it to offer good sound quality.

### Clock Sources

[Tmedia](/products/tmedia/tmedia.md) can synchronize its TDM network on 3 types of clock sources:

* BITS
* [Line Service](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/line-service)
* [SONET/SDH Interface](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/sonet-sdh-interfaces)

Clock type is determined by the Tmedia model. Clock availability is indicated in the following table:

| Models                                      | Clock Source Type | Clock Source Type                                                                                          | Clock Source Type                                                                                                         |
| ------------------------------------------- | ----------------- | ---------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- |
| Models                                      | BITS              | [Line Service](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/line-service) | [SONET/SDH Interface](https://tmediadocs.telcobridges.com/telecom-references/transmission-and-lines/sonet-sdh-interfaces) |
| [TMG800](/products/tmedia/tmg800.md)        | ✗                 | ✓                                                                                                          | ✗                                                                                                                         |
| [TMG3200-RJ](/products/tmedia/tmg3200.md)   | ✗                 | ✓                                                                                                          | ✗                                                                                                                         |
| [TMG3200-TE](/products/tmedia/tmg3200.md)   | ✗                 | ✓                                                                                                          | ✗                                                                                                                         |
| [TMG3200-DS3](/products/tmedia/tmg3200.md)  | ✓                 | ✓                                                                                                          | ✗                                                                                                                         |
| [TMG3200-STM1](/products/tmedia/tmg3200.md) | ✓                 | ✓                                                                                                          | ✓                                                                                                                         |
| [TMG7800](/products/tmedia/tmg7800.md)      | ✓                 | ✓                                                                                                          | ✓                                                                                                                         |

### Clock Redundancy

[TMG-CONTROL](https://tmediadocs.telcobridges.com/telecom-references/developer-reference/toolpack-api/tctrl) enables you to configure system clock references list using the [Web Portal](/other-pages/other/web-portal.md). Clock redundancy is accomplished by configuring at least two valid clock references in the system. [TMG-CONTROL](https://tmediadocs.telcobridges.com/telecom-references/developer-reference/toolpack-api/tctrl) will scan the clock references list until it finds a valid one. If the active clock source becomes unavailable, [TMG-CONTROL](https://tmediadocs.telcobridges.com/telecom-references/developer-reference/toolpack-api/tctrl) will select the next preferred valid clock source. Clock recovery, which means that the system will switch back to a more preferred clock source if it becomes available again, is an option that is available using the [Web Portal](/other-pages/other/web-portal.md).

It is worth mentioning that the [TMG7800](/products/tmedia/tmg7800.md) clock is distributed through the system using the TMS network.

The following image is an example of a [TMG7800](/products/tmedia/tmg7800.md) system containing 3 source references:

![TMG7800 System With 3 Clock References](https://docs.telcobridges.com/w/images/7/77/Ha_Clock_Setup.png)

Even if clock source #1 becomes unavailable, clock source #2 will synchronize the TDM network, as shown in the next example:

![TMG7800 System With 3 Clock References](https://docs.telcobridges.com/w/images/8/85/Ha_Clock_Setup_Failure.png)


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