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This guide explains the T1/E1 Port configuration for Digium VOIP gateways.

Logging in

  • Go to your gateway IP address
  • Enter your username and password
  • Click on Settings and Configuration
  • Click on T1/E1

General Settings


 Your locale. This will be used for the tone style used when in-call indications need to be generated such as ring back, busy, congestion, and other call-oriented inband tone signals.

Use Internal Timing

 Disable clock recovery from the T1/E1 spans. All spans use internal timing. 

For some devices such as channel banks this may need to be set to Yes

Clock Recovery Priority

 Select the spans to use for clock recovery and then prioritize the spans as to which should be used to recover the clock. (Priority 1 is the highest priority.)

Port Specific Settings

Click on the tab for the port you wish to configure.

Interface Type



Set your Framing and Coding to a valid pair. This information is usually provided by the provider. Most commonly this will be ESF/B8ZS


Set your Line Build-Out.

This is the distance from your T1 port to the providers equipment.  In most cases this will be 0-133 feet

CRC4 is not used in T1 and is disabled while in T1 mode


Set your Framing and Coding to a valid pair. This information is usually provided by the provider. Most commonly this will be CCS/HDB3


Line Build-Out is not used in E1 and will be disables

CRC4 is carrier dependent This information should be provided by your carrier. If things aren't working you may want to look at this setting.

Advance Interface Type

These items can typically be left alone


Line Signalling

This should be set based on your line configuration.  

For a PRI this would be set to PRI. For a channelized T1 you would set this to the appropriate RBS signalling type.

Channel Summary

This gives you a summary of the current channel setup. If you choose PRI as shown above it shows your B channels and D channels. You can edit the channels by clicking the pencil (unsaved settings will be lost). You would do this for example if you only had a partial PRI. You can go in and set the extra channels to "unavalible"

Setting signalling to a different mode will change the summary.

Signalling Role

This is for PRI and will be grayed out in other signalling modes. This is typically set to customer side when interfacing with a carrier. If you want to emulate a carrier you would set this to Network Side. This is the equivelent of pri_cpe or pri_net


National is pretty common on T1 but you will get this information from your carrier. 

EuroISDN is pretty common on E1 but you will get this information from your carrier. 

Channel Availability

Above in channel summery there is a pencil icon that allows you to set specific channels up.


On a T1 PRI your D channel will typically be 24 and the B channels will normally be 1-23. If you have a partial PRI your D channel will typically remain at 24 but your B channels may become 1-10.

Click on the pencil and you will get to the channel settings screen. Using the example of a partial PRI with 1-10 I select the additional channels

At the top there is a Modify Selected Channels dropdown

I am going to choose Unavailable

You will see the previously selected channels now say unavailable.

When you have the channels as you wish click Save Channel Settings

A popup will appear warning all calls will drop. Click Continue 

Now back in our port settings the summary will be updated.

Advanced Signalling

These items may typically be left alone.



When the port is as you would like it click Save T1/E1 settings.


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