Cisco VIC-2FXS or Cisco VIC-2FXO??

Unanswered Question
Oct 22nd, 2007


I'm building a Call Manager system in my home lab and I would like to verify which VIC card (FXO or FXS) that I should use in my Cisco 3640. This 3640 will serve as a gateway to my 2nd Comcast digital voice analog line. In my documentation it states that my analog connection at my house is considered to be FXO so I'm thinking that I will use a VIC-2FXS card. Also, do these cards support DID or do I need to purchase a VIC-2FXS/DID analog interface card?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Paolo Bevilacqua Mon, 10/22/2007 - 08:42


what is a "comcast digital voice analog line" ? If it is something to which you connect a telephone, the card you need is VIC-2FXO.

Note DID on analog lines is a special case so check with your SP first.

132061999 Mon, 10/22/2007 - 08:56


Thanks for your quick response! My local analog telephone sevice is being provided by Comcast cable. In my Cable modem are two analog ports which I have extended to my home phones. As for the DID questions does the FXO VIC card support inbound calls to the system?

mlitka Mon, 10/22/2007 - 10:34

An FXO card will support inbound calls into the system.

You will use an FXO card when you need to communicate with a device that is providing the dial tone. For example your "Comcast Digital Voice Analog Line" Since Comcast is providing you with dial tone the FXO card is the right choice here.

An FXS card would be used to provide dial tone to an analog device such as an analog phone or modem.

Paolo Bevilacqua Mon, 10/22/2007 - 12:16


I doubt that comcast supports DID on their adapter, but if they do then yes, the router would be able to collect and use digits.

Note that real DID on analog lines (sometime called trunks) works inverted, that is the user provides loop current (but no dialtone) to the exchange. Generally these lines cannot be used for outgoing calls.

jerry.bonner Mon, 10/22/2007 - 15:43

The S and O in FXS and FXO refer to what the port is facing. FXS faces the Subscriber (you). FXO faces the central Office (comcast).

If this is a normal service that you can just plug your phone into, then you need an FXO card for dialing out.

In your setup, you will most certainly NOT need DID support.


This Discussion