> 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/tmedia-documentation/configuration/setting-cas-r2-back-digits-variable.md).

# Setting CAS R2 BACK DIGITS Variable

#### ***Applies to version(s): v2.7.***

Once the CAS R2 stack and script are created, you must set the backward digits string to instruct the stack about the sequence of tone requests that must be sent when acting as the backward end. Refer to [CAS R2 BACK DIGITS](https://github.com/telcobridges-main/tmedia-wiki/tree/main/reference/protocols/cas-r2-back-digits/README.md) for more details. There are two methods to configure the backward digits string.

### Method 1: Setting script BACK DIGITS variable

The backward digits string can be configure directly inside a CAS R2 script. This means that all CAS R2 stacks using this script will benefit from the same configuration.

1- Click **CAS R2** in the navigation panel

![CASR2 0](https://docs.telcobridges.com/w/images/6/63/CASR2_0.png)

2- Click the **Scripts** tab

![CASR2 1](https://docs.telcobridges.com/w/images/f/f3/CASR2_1.png)

3- Click **Edit** next to the desired configuration

![Toolpack v2.5 Edit User Scripts](https://docs.telcobridges.com/w/images/7/7e/Toolpack_v2.5_Edit_User_Scripts.png%E2%80%8E)

4- Edit the "**BACK\_DIGITS**" variable value to the desired value, please refer to [CAS R2 BACK DIGITS](https://github.com/telcobridges-main/tmedia-wiki/tree/main/reference/protocols/cas-r2-back-digits/README.md) for description of valid digits.

![Toolpack v2.5 Edit Scripts Back Digits Variable](https://docs.telcobridges.com/w/images/3/36/Toolpack_v2.5_Edit_Scripts_Back_Digits_Variable.png%E2%80%8E)

### Method 2: Setting stack BACK DIGITS variable

The backward digits string can also be overwritten on a per E1/CAS R2 stack base.

1- Click **CAS R2** in the navigation panel

![Toolpack v2.5 Navigation Panel CASR2](https://docs.telcobridges.com/w/images/c/c8/Toolpack_v2.5_Navigation_Panel_CASR2.png)

2- Click **Edit** next to the desired stack

![Toolpack v2.5 Edit Casr2 Stack](https://docs.telcobridges.com/w/images/8/83/Toolpack_v2.5_Edit_Casr2_Stack.png%E2%80%8E)

3- Click **Editing Variant Script Variable** to expand area

![Toolpack v2.5 Casr2 Stack Variable](https://docs.telcobridges.com/w/images/f/f0/Toolpack_v2.5_Casr2_Stack_Variable.png%E2%80%8E)

4- Click **Create New Variable**, select **BACK\_DIGITS** variable name from the drop box and enter the desired value

![Toolpack v2.5 Casr2 Stack Add Script Var](https://docs.telcobridges.com/w/images/9/91/Toolpack_v2.5_Casr2_Stack_Add_Script_Var.png%E2%80%8E)


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