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New Member

T1 CAS E&M ANI question

Primary question:

With the following statement from the Cisco Docs "T1 CAS fgd is asymmetric. When calling the switch, we only generate DNIS. When receiving from the CO, we get both ANI and DNIS", is there any way a T1 CAS can be set up to send Caller ID (ANI) or in other words, DOD?

Secondary Question:

Is it true that the only difference with Caller ID and ANI is that with ANI, only the phone number is sent, but with Caller ID, you get the number + station name or ID.

New Member

Re: T1 CAS E&M ANI question

Hello Matthew,

ANI is associated with trunks either over Q.931 or using FGD (MF) over E&M. ANI comes to the called party user (end point) via Q.931, which implies an ISDN device. ANI is passed through the telco network via SS7.

CID caller ID is the transmission of the calling number in the 4 second silent period after the first ring of the phone call to the called party end point. This is the typical caller ID used in the USA.

I don’t know about your primary question.


New Member

Re: T1 CAS E&M ANI question


You cannot do ani authentication with a cas line. CAS lines do not carry near as much signalling information as PRIs. There is no way that cas can carry ani information. I used to work for a VoIP of our clients wanted caller id. Most calls went "off-net" through an as5300 to the pstn. Our own company used cas in the state we operated in. Because of that....customers could not automatically be authenticated via ani. They had to enter in a pin number to be authenticated before they could make their call.

As to the caller id and ani question. All I can say is that they are totally different. We had a client in a different state....who when setting up some pris, thought by automatic number identification, that we meant caller id. (Some provisioners call it calling named or name id so be carewhat what you call it....they have numerous different names for things and it can wreak havoc with configuration.) Because of it, they turned caller id on and it created several days of troubleshooting....when they realized we didn't mean caller id....but ani.....they were able to get the pri to operate perfectly in no time at all.

As to the technical difference between ani and caller id....I don't know the real technical distinction.

New Member

Re: T1 CAS E&M ANI question

Hello Jim,

R2 CAS signaling has ANI as part of its standard. It is carried as a MF (multi-frequency) as a part of FGD (feature group D). I have not seen this implemented in this country (I am not a telco guy). I refer you to Scott Keagy’s excellent Cisco Press book “Integrating Voice and Data Networks”.


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