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New Member

fxs config

I have a remote gateway with an fxs card in it. I have created the dial peers on this gateway to call extensions back at the main site- this works ok.

for this fxs device to be able to call external numbers , do I just need to have a 9.T dial peer point at the CM , and a CSS on the GW to see the routepatterns.

also If I wanted to insert a credit card manchine into the FXS port (which has a built in modem to dial out) do I need extra config on the GW to support this?


Cisco Employee

Re: fxs config

Yes, you need a 9.T pattern and it should point to the CCM. Now, make sure your CCM is aware of this GW, which means you have to configure the GW on the CCM.

For modem to work, you have an extra task. You need to configure modem passthrough. It can be accomplished by

conf t

voice service voip

modem pass nse pay 110 c g711u


Hope this helps

New Member

Re: fxs config

I entered the commands above, but I still can't get the modem to dial the number successfully, when I plug a phone in it works fine.

Any suggestions



Re: fxs config

You would need to enable modem commands on the gateway at the other end also.



Cisco Employee

Re: fxs config

I think he has a CCM on the other end doing H323.

You will need to look at all the GWs the call traverses and in the CCM admin page, check the appropriate boxes for

"enable modem calls on the GW"

"enable modem passthrough"


New Member

Re: fxs config

Thanks for you help guys,

There is a ccm on the other doing mgcp,

I have checked all GW and all modem commands are there,

where do you "enable modem calls on the GW" in ccm likewise "modem passthrough"

on the actual credit card device, the light of the FXS port comes on each time the modem attemps to dial, there is a com error on screen.


Cisco Employee

Re: fxs config


So, at this point, we need to determine if the following things happen:


When TGW detects the v.21 fax tone from the terminating fax machine, do we switch over to cisco fax relay or do we try to do passthru. relay usually has more failures than passthru.

If one end is configured for passthru and the other end is configured for relay, we will have issues.

The following debugs will tell you what might be going on:

debug voice ccapi inout

debug voip vtsp all

debug voip dsmp all

look for the word "detected fax tone" in the vtsp debugs, and then check what happens.

I want to find out what your two gateway platforms are. Also, along with the debugs, send us a show ver and show run.