FXO and FXS - I'm confused 1

[dudecrush]

All - I added one FXS (VIC3) card and one FXO (VIC2) card to my 2911 router. In my mind, I intended the FXS to be used for a fax machine and the FXO card to be used for an emergency-dial POTS line if connection to call manager is cut. I had the Telco install a POTS line for the emergency dial, and had it extended from the demark to the server room.

Once added to the router, I designated which slot the FXO & FXS cards occupied to the appropriate MGCP gateway in call manger. Unfortunately, I couldn't complete the setup for my FXO card because it was asking me for an attendant DN to associate it with. I found that strange, because I think of FXO as external...something provided by the phone company. Thus an attendant DN isn't necessary because the number is already decided for you.

What turned my world upside down was noticing the FXS card provides the port option for POTS - and doesn't require an attendant DN for config. So now I'm thinking my emergency line needs to be added as an FXS instead.

So my questions are:
1) Do I have the concept of FXO and FXS reversed, or am I just missing details?
2) For the emergency POTS line, do I assume the wall jack is an FX0 port and thus configure my emergency line in my call manager gateway as an FXS port?
3) Would I configure my fax line as FXO or FXS? The fax itself is internal, I just want to associate the DN from a CTI route point to the router. I keep thinking FXS but I'm now 2nd-guessing myself.

Any help is appreciated.

 

[gnrslash4life]

1. No you are correct in your thinking.

2. You want your POTS line in the FXO port. You can make the Attendant DN whatever. Usually I just make it the number I am programming. Thankfully they got rid of it in later versions.

3. In your case FXS.


FXS ports provide dial tone, FXO ports do not. Since a POTS line provides dial tone itself, you dont need a port do that so you hook it up to the FXO port. Since you have an analog device that needs dial tone internally, the only way to do that is to hook it up to an FXS port.

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[dudecrush]

gnrslash4life - Good call. I thought I was going insane. A few other questions:

Emergency Line / FXO Port:
a) Port Type: I would assume ground start (to avoid glare - since they'll need both inbound and outbound calls on the emergency line)
b) "Product Specific Config Layout" (Hookflash timer, echo cancellation, etc.) - I presume these can be left to default
c) Incoming Calling Party Settings - All set to default. I don't think I need to strip digits or any another thing.


Analog Line for fax / FXS port:
a) Port type: POTS, Ground or Loop? (I'm assuming POTS)
b) Port Info - POTS: Number of Digits and Expected digits. We use 4-digit dialing internally, and there are a lot of "4-digit" faxes sent between departments. That said, this fax will also receive the typical 7 and 10-digit calls as well. If I put in 10 for number of digits, will that cover the 4 and 7-digit faxes, too?

 

[gnrslash4life]

A) I would use ground.
B) Most likely are ok for default.
C) Should be fine at default then.

A) I would use POTS or Ground should work fine too.
B) I dont recall seeing this on an FXO port. What version you running?

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[dudecrush]

It would be for an FXS port, not an FXO port. That said, we're using CM version 9.1.

 

[gnrslash4life]

My bad. Read it wrong. Anyhow, I leave my default which is 0.

Certifications:
A+
Network+
CCENT
CCNA Voice
TVOICE
CAPPS

 

[dudecrush]

I figured, but no biggie. I knew what you meant.
Your advice was spot-on, so I gave you a gold star. Thanks bud.