atcomsystems.ca/forum Forums VOIP Phones & IP PBX VoIP & Cloud Phones, Hosted PBX, General IP Phones Analog modem over VoIP

I occasionally have to use a dial up modem to do programming on some PBXs. I am thinking of going to phone service in the house provided by the local cable company. Has anyone used this set-up before with dial up modems ? Any problems?

Thanks

I know many people in this area that went to cable for phone service and switched back because modems and faxes wouldn't work correctly.

Thanks - am doing some research on it right now. Seems if the local VoIP provider supports ITV V.150.1 on their network then I shouldn't have a problem. So I am trying to find that out from them right now. Thanks for the quick response.

I think what matters is if the CATV provider is using VOIP to provide dial tone or if it is just multiplexed analog. It is true that if VOIP is the medium, you probably will have modem issues unless you are working at very low baud rates.

Dane, have the provider set their "cable modem" to work with a "fax". TWC now furnishes "fax" connective modems from thier cable to supply dial tone that does work with faxes. The modem you want to use "should" work over the line the fax does......

With that being said, good luck or get a copper land line for it.

Well no sense going to the additional expense for a cooper line just for occasional use. The techie at Bright house said they were ITV V.150.1 compliant so I think it will work okay but I will check to make sure that fax will work since I have to send one of those every now an then. Thanks for the suggestions

I have had all sorts of problems with VOIP-type service to us (Frac T-1 by PAETEC). We installed a separate POTS line from PAETEC because they couldn't get the other lines to work with modems right. The "POTS" line didn't seem to work right either. I now have a POTS line from AT&T that I use for modem work---and it seems to work a lot better. However, particular modems are a problem. I get much better results from an external modem. The internal ones work fine sometimes and don't work at all other times. I have no idea why they are like that.

Most of our phone systems have internal manufacturer-provided modems---so they are all the same. Some of our other systems (like Mitel) have external modems that run through the systems and use the customers VOIP service. So that is a factor too, it seems.

It's all a crap shoot. It can be very frustrating. I continue to work and tweak things so that I can at least tell what and why things happen...it's taken me years & years. I still have a lot to learn, I'm afraid. Every location is a bit different.

10 years ago, things were a snap. Set up the modems, plug them in and bang---you could use hyperterminal all day loing and never have a misfire. Now it's a crap shoot.

Best speeds I've been able to achieve on VoIP with fax/modem was 9600bps. Real world was more like 2400 or 1200. That was fine for credit card processors but most faxes ended up getting a copper pair from the LEC.

having to modem into a pbx over copper pots can be a crapshoot at the best of times,

doing remote config of a pbx is best done via an IP connection, or better still with centralized voip systems, via a web portal back to a data center.

One reason for this is probably because many external modems include a coomunications controller. Most internal modems hand off comm functions to the main processor or the onboard input/output chipset which is doing many other things as well.
For critical applications, get either an internal or external controller-based modem. Figure about $100 and up for the external.

ITU 150.1 is the standard for interoperability between modems and other data equipment over IP. (That's separate from Fax-Over IP). If, a BIG if, the provider(s) have implemented it properly, your modems should work.

ITU 150.1

To add to my post above, some modems with onboard controllers/DSPs:

Multitech Multimodems (I think all of them have onboard controllers and/or DSPs).

USR Courier Business (I've used the "V.Everything" model)

Hayes Optima (I think some of the Accura models are controller-based too)

Some of the old async Paradyne models, though they never made it to the latest standards.

If you don't want to pay $$$ for analog dial-up (though some of them work over 2 and 4 wire sync/leased lines as well) there's always ebay.

It really depends on the type of compression that the VoIP carrier is using. If they are using something like CELP (code excited linear prediction) for example it will pretty much destroy your data since a lot of codecs were designed around the principle of the majority of a conversation is silence. Nyquist's rule states that your sampling rate must be twice the highest frequency in your data in order to accurately reproduce it and compression codecs don't follow that.

Works great for voice because our ears are crappy in the great scheme of things, but data suffers because it is not comprised of mostly silence. There is a heck of a lot of difference between voice audio and a QAM stream.

If the VoIP carrier uses Mu-law (G.711) it's usually going to be alright because it follows Nyquist. That can be somewhat rare to find because it's a whole heck of a lot of bandwidth to use when they can usually squeeze a lot more on to their carrier groups with compression and with 99.99% of your usage being for voice they don't worry much about data (and faxes transmitting at slow speeds doesn't matter so much as long as they successfully transmit).

The other challenge is that most VoIP providers have a very, VERY limited understanding of voice which causes an uphill battle for most anything.

The problem is not with the standard, Modem-Over-IP has been in force since the turn of the millenium. It's with the fact that for most providers there is no pressing business reason to offer the service - the demand for this is just not there for most users (home or/and small business users). If the ISPs/CLECS do offer this, it is often sloppily implemented with inferior equipment, oversold nodes, non-specialist personnel (=bad configurations) etc.

The major, business-oriented providers, do offer Moip (V. 150.1) either a la carte or as part of their IP bundles, and they implement it properly to the point where it is transparent. Their customers usually have (still) big investments in dialup communications of all kinds (don't forget that the first application for end-user DSL was "always-on ISDN" - IDSL). The big boys' offerings ofcourse are considerably more expensive across the board.