VoiceT1 CAS - Loop start

Unanswered Question


I have a Voice T1 circuit running loop start signalling. I do not know how to configure the Controller T1 interface on my 3825 router.

Has someone does this, please help me with the commands.

I tried

controller t1 0/1/0

dso-group 1 timeslots 1-24 type dfd

framing SF

linecode B8ZS

Thanks in advance,


I have this problem too.
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Hey, thanks for the links the last one was very informative.

It only tells me that I can use either

ds0-group 1 timeslots 1-24 type e&m-fgb (OR)

ds0-group 0 timeslots 1-24 type e&m-fgb dtmf dnis

or other types, but I do not know what I need to use for LOOP START.

Is there a particular ds0-group TYPE that I need to use???



Paolo Bevilacqua Mon, 06/11/2007 - 06:25


Is the T1 line from a telco switch, and the router "pretends" to be 24 telephones ?

If so, type should be fxo-loop-start.

Paolo Bevilacqua Mon, 06/11/2007 - 06:58


If telco has given to these lines one or more numbers that you can call from any telephone, then yes these are fxo-loop-start.

Note this is a type of singaling that can give you problems because of lack on disconnect supervision (among other things), so if you want things to run really smooth and easy, ask telco if they can make the circuit to be ISDN PRI instead.

Hope this helps, please rate post if it does!


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