> 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/transmission-and-lines/klm-vs-itu-t-vs-alcatel.md).

# KLM vs ITU-T vs Alcatel

There are two modes of STM-1 virtual tributary channelized interface mapping. They are the ITU-T mode and the KLM mode.

The below examples shows the STM-1 de-multiplexing scheme for: STM-1 -> VC4 -> VC12

1. Create the STM-1 line. Click on "Line Interfaces". Then click “Create Multiple Line Interfaces” on top of the page

![STM 1 LineInterfaces](https://docs.telcobridges.com/w/images/0/05/STM-1_LineInterfaces.png)

2. Create one STM1 line with payload type “AU4”, and then click “Create” at the bottom.

![STM 1 CreateMultipleLineInterfaces](https://docs.telcobridges.com/w/images/2/29/STM-1_CreateMultipleLineInterfaces.png)

3. Click “Create Multiple Child Line Service” on top of the page. Create one line service for the VC4 with payload type VC12, and then click “Create” at the bottom. ![STM 1 CreateVC4LineService](https://docs.telcobridges.com/w/images/5/59/STM-1_CreateVC4LineService.png)
4. Click “Create Multiple Child Line Service” on top of the page again. Create 63 line services for the VC12 with payload type E1s, and then click “Create” at the bottom. When it finished, click "Save".

![STM 1 CreateVC12LineService](https://docs.telcobridges.com/w/images/9/94/STM-1_CreateVC12LineService.png)

5. Click "Edit" next to one of the newly created E1 child line services.

![STM 1 ChildLineServices](https://docs.telcobridges.com/w/images/f/fd/STM-1_ChildLineServices.png)

6. Click “Create Multiple Child Line Service” on top of the page. Yes, again. Select all the VC12 line services.

Select **KLM**, **ITU-T** or **ALCATEL** for VT channel assignation, then click “Create” at the bottom.

![STM1 klm itut alcatel](https://docs.telcobridges.com/w/images/4/4d/STM1_klm_itut_alcatel.png)

7. After creation completes, click “Save”. The STM-1 line has been successfully configured.

### References

* [Channelize\_STM-1\_to\_E1\_Channel\_Mapping](https://github.com/telcobridges-main/tmedia-wiki/tree/main/reference/transmission/channelize-stm-1-to-e1-channel-mapping/README.md)


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