Noob Questions... Asterisk with Cox Digital Telephone?

Hi there. I’m very interested in installing Asterisk in our home office, and have read through the docs, etc. but really am not grasping the options that would best suit us for connecting it for our needs.

Here’s some more information… I run a small software company, and we are VERY Linux savvy. However I’ve never connected any phone systems to VoIP, etc. having always relied on the phone companies to provide us with the phone services. The problem is that as we grow, I’m finding the local phone company offerings to be way too expensive and way too limited.

We have 3 businesses running out of our home office. All of these businesses need their own phone number. However once the calls come into the home office, they route to the same phones, but just need to be identified as to the origin. Right now we have multiple phone lines from the phone company and use a Call Transfer facility from an old computer based phone system that I cobbled together, with one computer for each incoming line. I’m trying to consolidate this so that it will all run through one Asterisk system.

I’m probably asking for a lot from Asterisk here, but being a programmer I’m willing to code it so that each line can have its own Call Attendant system (phone menus, etc.), music on hold, and call transfer. I’m really trying to remove the phones in the house and turn them into IP Phones so that I don’t have to pay this ridiculous monthly phone bill all the time.

From what I have read, it seems that a VoIP connection to Asterisk would be the right way to go. But how does one organize this? I just made a call to Cox Digital Telephone, who provide us with service for one of our phone lines, and they are saying that they can bring a dedicated line to the building with a DMarc (sp?) but after that its up to us what we do with the connection. The price was reasonable, but I’m not sure if this is what I should be getting?

Anyway I know I’m asking a lot of questions, but I’m hoping some kind soul could point me in the right direction of where to look, research or share their story of how they got a similar system up and running and what I should look out for. At this point I haven’t bought any hardware for this, but am ready to get started once I have the strategy for this properly defined.

Thanks in advance for any pointers, advice or info.


You could do the following;

Get yourself a good VOIP provider that has incoming service with numbers available in your area code. I haven’t looked into this, but they may even be able to port your existing numbers over to their service.

Set up your Asterisk box with SIP hard phones to all your people. I run the Grandstream GXP2000 at home and love that phone - others hate it, but bang for the buck is extremely high. These phones have 4 line appearances each so you could set each incoming number to ring a particular line, do custom ringtones, etc.

With Asterisk running it all, you can set up VM, auto attendant, transfer calls, music on hold, etc. etc. all with just some coding.

Another option would be to setup your asterisk box with internal phone cards (Digium preferably but there are others) with FXO ports on them for the 3 existing lines you have. Personally, I’d still get a VOIP provider for your outgoing calls (thinking long distance here) as you’ll pay a lot less than your local telco charges. For example I’m using right now and they charge 1.2 cents per minute to any phone in the US. Downside is they are only for outgoing, no incoming calls.

I hope this gives you some ideas to get started. I’m a noob myself, but it’s all come together for me pretty well and I love the system so far!


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Major, major thanks for your input on this. A few questions…

Get yourself a good VOIP provider that has incoming service with numbers available in your area code. I haven’t looked into this, but they may even be able to port your existing numbers over to their service.[/quote]

That was my hope. I have a decent broadband Internet connection here, but I wanted something that would be dedicated for phones as I’ve tried Vonage for this and the service just plain doesn’t work on my current Internet feed. We have Cox here for our cable Internet, and they have provided me with digital telephone before. Do you think that a cable ISP carrier like this would offer such a service? If so, what do they typically package these services under? I called them today but the person on the other end of the phone really didn’t know what they were talking about, so I’m not sure what to ask for.

That sounds just like what I was thinking of doing. I think that if all of the 3 lines can come in through the one VoIP carrier, then we can just use SIP phones on the house for the voice calls, and drop a bunch of other phone lines (and their bills).

Yep, this is where I feel most comfortable (being a programmer). Its just working out the VoIP stuff that I’m a total noob at.

That may be an option for one of the lines if I can’t port the number over. We have a main business number that I don’t think will port, but I’ll see what can be done with other VoIP carriers here once I identify my options.

Absolutely helpful! Thanks again for your post. I have a few details to work out, but I think I’m grasping it a bit better now.


I am highly doubtful that Cox would supply you with VOIP service in a generic sense. I do see them offering their own branded service with an ATA etc. but it probably wont integrate with Asterisk very well. Their service is to provide a standard POTS type connection just like the phone company would. Asterisk connectivity is probably a little too sophisticated for them.

Hmm, Cox doesn’t work with Vonage very well at your site? I’d set up a small Asterisk box and do some serious testing before doing any big investments. I wonder if Cox is running some filtering etc. to screw that up. I think there are some lawsuits against one of the big cable companies for doing this right now, hopefully they win and the cable companies stop this kind of thing.

It sounds like you’re headed down the right track. Again, I’d do some serious testing before jumping in head first, especially with your bad Vonage experience. Good luck!


When I called them yesterday, the girl on the phone said that they can do it, but she said what they do is run the line to the building and terminate at a ‘Dmark’(sp?) and then its up to me what I do with it. Now what all that means, I have no idea. She did quote that provisioning a phone number costs $24.95 per month per number.

Does any of that make any sense?


Dmarc is a spot on the wall where the phone company (cable company in your case) brings a line into your home or office. To me, this appears as though it will be a standard analog line (but ip in the background). Yes you could connect this line via an ATA or an internal card with an FXO port, but I still think you’re better off finding another VOIP provider to connect up with.

This Cox solution is a lot like a Vonage solution. They drop a “box” into your house that you can plug your analog phone into. I’d bet dollars to doughnuts if you called up Cox and told them you wanted a SIP connection to your Asterisk box for telephony - you’d hear crickets chirping in the background. Yes, they can give you a “phone line”, but that’s just it - an analog “POTS type” phone line and that is all.

I’d also bet that you can get a better deal than what Cox would give you with another provider. You could also get 800 lines etc. Here is some quick math I did when I was deciding whether I should go with a Vonage (or Cox) type solution, or roll my own with a 3rd party VOIP proider. Keep in mind, in my situation, I need outbound long distance only.

Vonage/Cox = $24.95/month unlimited long distance (US) = 1.2 cents per minute long distance (US)

so 24.95 divided by 1.2 cents per minute = 2079 minutes = 34+ hours.

That means I’d need to spend more than 34 hours per month on the phone long distance for the Vonage/Cox solution to be worth my while. No brainer on my part as I don’t come anywhere near that amount. Granted you’ll need incoming as well so you’ll need to run the numbers for yourself on this.

Also, you could do both, use the Cox line for outbound calls and get yourself a VOIP provider for your additional lines. I don’t know how well the Cox line would integrate into your solution, but that is somewhat what I’m doing right now. My setup, I use a VOIP provider for all my outbound calls, and have a local line with my phone company for incoming. I do this as I must have a local line for my DSL connection. They claim I cannot “unbundle” the phone from the DSL so I’m stuck.

I feel like I rambled a bit there. But in summation - no Cox will not provide you with a SIP VOIP solution that easily ties into Asterisk. Yes you can probably use their “line” but it would be like any analog phone company line and you’d need to add an ATA or internal FXO card to your system.


Again, thanks so much for your detailed answers.

As I understand it, you are saying that despite Cox saying that they will bring a dedicated IP connection to the building and terminate at the DMARC, its up to me to find a way to connect this to the Asterisk box, and if I understand you correctly, it would be just as easy to have them give me phone lines and numbers as PSTN lines, and use a FXO card in Asterisk to handle incoming calls through that.

That’s ok, and probably would be a cost saving for incoming calls. What I would gain would be the cost saving if I switch the phones internally all to SIP phones and use our LAN to handle multi-channel communications through Asterisk. And if outbound calls can be routed through our existing data network, I suspect that would keep the costs of calls down.

Am I correct in understanding your post here?


You’re close. The dmarc is where they bring in the analog phone line. If it was a VOIP sip line, they wouldn’t need to bring in anything as that goes over your existing internet connection to them. When they “bring it in to the dmarc” they hookup some kind of ATA (analog telephone adapter) to your existing cable lines/network to give you analog dial tone. There wont be any “ip termination” at the dmarc, it will be an Ethernet cord or cable line to their “box” that has a phone jack in it, no matter what this rep is telling you.

If you were to then hook this up to your asterisk box, you’d need another ATA box to do it, so it would look like this

-----> IP -----> Cox ATA box ------> Your ATA box ----> IP ----- Asterisk.

If they were a true VOIP provider your connection would be;

-------> IP -------> Asterisk

much simpler and less messy. Skips two conversion steps from IP digital to analog, and then back from analog to digital. All those conversions can introduce ugly things like echo into the line. If I were you I wouldn’t even consider Cox phone service IF I could get reliable VOIP services over the internet from another provider. Cox service would be good for mom and pop, but not the kind of things you want to do.


Major thanks again. I think I got it this time.

I agree that a VoIP->SIP connection would be the best option for me. My problem, however, is that the only Internet service we can get where we are located is through Cox. So either way, I’m limited to using them to provide services here.

I’m thinking that since I have had relatively good results with their digital phone service, that I might use them for 3 numbers coming in, and do the FXO card for this, since reliability and QOS is the most critical thing for me. Yes, I do want to program the phone system extensively. And Yes, I want to be able to make outbound calls via a VoIP provider, but I really need a high quality phone experience for my customers.

Am I being too conservative here? Is it that my bad Vonage experience is skewing my brain in a way that it shouldn’t be?


You sure can go ahead as you have planned. Again, start small and work up. Get one incoming line to Asterisk (via your FXO card) and play around. Good luck!