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Using DSL Modems for Point to Point Connections?
Tommydog asks: "Any techies out there? I'm living in a rural area and would like to know from anyone qualified, if I can hook up 2 DSL modems point to point, and connect to a neighbor's home network who is running Internet Sharing. We do have a dry pair (we can only get one pair) of TELCO wires between our houses, which are about 2 miles apart. Before investing in a couple of single pair modems (T-1's require 2 pair), I'd like to know if anyone has been able to make something like this work. It turns out that I'm just a bit too far for DSL, but this neighbor does have it and will share it if I can get a good connection going. So, anyone have 2 DSL modems working point to point, back to back? Are there any caveats or precautions? Thanks!"
Are there any caveats or precautions?
You may have already considered this, but most ISPs that I'm aware of have a line in the ToS that states that you may not share the connection with other people. And they do check; I remember a friend getting his house checked by Road Runner due to his daughter using P2P out the wazoo.
This statement is false.
There's an article on I, Cringely that describes this exact scenario.
However, he wanted to sit in a coffeeshop in town and use his home network, so he claims he installed a couple of high powered "pringle antennae" climbed tree, installed another one as a repeater in a tree somewhere (to get around a mountain) and he was in business. Shouldn't be too hard to line-of-sight something 2 miles.
http://www.pbs.org/cringely/pulpit/pulpit20010823. html
I've had enough abrasive sigs. Kittens are cute and fuzzy.
I have done this before. The best I could ever get it to work was for 22K feet. The thing you need is two DSL modems that can speak together. Most of what is being sold today expects an expensive backend CO unit and a cheaper frontend modem.
I suspect that if you want to do this cheaply you would be best off finding an ISP that experimented with "rolling its own" around 1998-99.
You can't grep a dead tree.
Sharing the connection is probably against the DSL provider's terms of service. Your friend might want to look into that before sharing the connection.
most telcos are clued into the 'dry pair' (whatever you wish to call it) orders, and will deny them.
a tech for sbc (who i have no reason to believe was lying - we were speaking friendly at a resteraunt) told me that they screw with service on local lines and can cause techs to get electrocuted because the lines aren't flagged.
Speakeasy does allow connection sharing. The DSL line owner is responsible for all activity that occurs on the line naturally.
you can not send enough power to electrocute someone over a low guage phone pair. get real.
But assuming that you own the property in between...
Have you considered putting in a fiber link? On ebay, I just saw a 9k ft spool for ~$200 buyitnow awhile back. $30 for some 10baseT transcievers at each end. Renting a trencher for a weekend would cost what? Hell, it might be alot of work, but in 2 years when you decide you want a 100baseT link, or even gigabit, you buy some more (by then) cheap transcievers. For that matter, you might even be able to find the equipment to multiplex cable tv over the damn thing, if you wanted.
Just a thought.
Maybe not enough power to electrocute someone, but there is enough power on a phone line to cause a tingle (especially if you touch the bare copper while a ring is sent through). Thing is, dry pairs aren't the only ones that can do that... all lines can do that.
If you're thinking of running a phone line from your neighbor's house to your house....
Why don't you just use plain ethernet? 100 feet is the maximum cable length, but if your neighbor is next door, it's definately the easiest way.
keep poking your test leads into the can, you should find another dry pair for the Telco to, ahem, 'lease' to you.
i dont suppose you have any sort of cable (ie co-axial) connection running down those poles do you? might be able to get a dry line there and convince an old BNC'd ethernet card to shove data down it.
also remeasure your distance. is he two miles straight down the road or two miles across a field and thru the woods?
looks around im sure ive seen some people using microwave, wi-fi, laser, and radio over those distances jsut in case your DSL doesnt go.
yea im sure this post helped you a lot.
BTW, if your phone company won't take your order for a "dry pair," ask for an "alarm circuit."
You should be able to just plug both of them in, configure your TCP/IP stacks to use the DSL "modem" as a gateway, and you're off to the races.
I think a ring is 90v AC. Don't remember the frequency, though, and I could be wrong, so don't quote me on that ;)
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Well, yes, neat trick, saves you from putting the wires in.
But this guy already has the wires.
Maybe it would be easier for him to use them.
"I believe that the cult of the particular brings only death - for it bases order on likeness." St.-Exupery
Go to http://www.paradyne.com/ and check out their Etherloop 1020 modems. I'm not sure if they technically use DSL signaling, but they work GREAT. Up to 10 megabit and up to about 22,000 feet (I think) range. Bandwith drops as distance increases a bit, but it blows most DSL out of the water on range and bandwith.
We are currently using them to phase out some ISDN lines. At $175 a pop (need 1 on each end) it's pretty economical. Currently "modem to modem", but we have some actual DSLAMS were going to be installing shortly.
They will work on just a dry pair, or a pair with tone on it. The builtin POTS splitters work fine, even modem to modem. The only issues are getting access to the cabel plant... not that big a deal for "us" as we are on a military base and own the plant, but probaly dificult for normal telco lines.
Their documentaion is kind of poor, but the products are great. You have to call them and track down a re-seller which is a pain, but worth it.
here's a quick guide to DSL:
there are many types of DSL... ADSL, SDSL, HDSL, VDSL, SHDSL, etc. they are divided into 2 main groups: Symmetric and Asymmetric.
the "symmetry" of a DSL modem refers to the way the frequency spectrum is divided up. above the voice spectrum, there is an upstream data spectrum followed by a downstream data spectrum. in Asymmetric DSL types, the upstream spectrum is much smaller than the downstream spectrum. in Symmetric, they are the same size.
since ADSL modems have different size spectrums for upstream and downstream, they do not connect to each other.
Symmetric modems, on the other hand, are more readily connectible to each other. but, most need to be configured so that one will act as the "central office" device, and the other will act as the "consumer premise" device.
the other thing that needs to happen in order to connect symmetric devices is configuring the ATM settings properly. DSL devices use Asynchronous Transfer Mode to transfer data across the line (this has nothing to do with your local network). most devices use a PVC of 8/35; it doesnt matter which one you use, as long as they're both the same.
so, your best bet would be to use two Symmetric modems with consoles that you have access to.
Somewhere on this page I have hidden my signature.
Amps?
A static shock has a bajillion volts, but not much amperage.
analogy:
"Man, there was this guy, in this massive water pipe! He could have gotten killed!"
"Was there any water in this pipe?"
"Well, a trickle on the bottom, but it was a HUGE PIPE!"
I will now redundantly add my name to the end of my post. You know, in case you forgot me or something.
Amps?
Enough to cause the muscles in my arms to rapidly contract. When I was a little kid, somewhere between 8 and 10, just getting into lower level electronics, I didn't know what the voltage was on a phone line, and so I was stripping live phone line wires with my teeth (my parents wouldn't buy me strippers) to run a cable to my modem, and the phone rang. Yow!
A solution to the problem with music today
If you want the consumer-grade stuff (the 3com or dlink RTUs that you buy to hook up to your telco's network), then no. They need a DSLAM.
If you want to spend a few bucks ($1000 per end), Adtran makes some good HDSL gear - such as the Express-L768, and Express-L1.5, that will do what you want. The L-768 is probably what you want, as it uses a single pair, and runs 768K bidirectional. (The 1.5 runs at 1.5M, but uses 2 pairs.. it can also run 768K on a single pair.)
We use these at a number of sites, and they work pretty well.
There are caveats.. the maximum distance you can drive them is 18000 feet.. and if you're leasing copper from the telco, you have to watch the distance.. the telco here bills length as crow-flies distance, so unless you know their distribution network, you may not know the exact footage.. for example, we have two schools that are about 3 feet away from each other (next door), but the actual cable distance was over 20000 Feet. (The copper for each site runs back to the telco's distribution point.)
If you own the land between the sites, I'd do as another poster suggested, and run fiber)
Poor kid, parents wouldn't buy him strippers.... Then again, what parent ever does buy their kid strippers?
;)
If my parents had bought me strippers...
Yow!
"you can not send enough power to electrocute someone over a low guage phone pair. get real."
You should get real. It requires very little 'power' to disrupt the heart. The resistance of the skin is what usually keeps this from happening. If you have bare dry hands, you're probably right - but:
The C.O. will send enough voltage to make an old-style mechanical ringer operate. It's a constant-current source (ie: it will raise the voltage until the appropriate current flows). With no phone on the line, you'll get maximum voltage as the C.O. attempts to make the electrons flow.
Again, the resistance of your skin is the deciding factor. Get your hands wet, or let the wires pierce your skin at the same time the C.O. decides to ring your phone and could could easily become dead (remember to hold one wire in each hand if this is your goal).
As a reference (current in *milliamps*):
Unsafe current values:
8 mA to 15 mA
Painful shock; individual can let go at will since muscular control is not lost.
15 mA to 20 mA
Painful shock; control of adjacent muscles lost; victim can not let go.
50 mA to 100 mA
Ventricular fibrillation - a heart condition that can result in death - is possible.
100 mA to 200 mA
Ventricular fibrillation occurs.
200 mA and over
Servere burns, severe muscular contractions - so severe that chest muscles clamp the heart and stop it for the duration of the shock. (This prevents ventricular fibrillation).
http://www.elec-toolbox.com/Safety/safety.htm
A.
...bringing you cynical quips since 1998
I own a very small ISP in rural North Carolina. We started it mainly to allow us to have broadband in our programming office.
Until about a year ago, Sprint would allow us to order these point-to-point dry pairs. Since we didn't have any other type of broadband (except Sprint's "reasonably priced" frame-relay circuits ~$700 for a fracT1) we used these circuits with PairGain 300S sDSL modems. These are manually adjustable from 128kbps up to 2048kbps depending on the distance and quality of the lines. They work very well. We were able to use them with circuits approximately 2-3 miles long at speeds of 384kbps and in one case the line quality was good enough to support 768kbps.
There is a huge difference between a modem and 384kbps circuit. I highly recommend them.
That being said, these modems are very expensive. I haven't priced them in several years but they were about $900 for a pair a couple years ago.
Phone service runs at 90V 60Hz A/C here in the US.
The amperage is enough to ring your phones - there's no circuit breakers inside the customer's house, so they'll suck as much current as they need. The lack of a breaker is because it's really typically not needed for residential use - phone lines only have high voltage during the short burst of each ring. The rest of the time there's just low signal voltage and extreme low current.
US electrical code requires 14GA cable for 15A and 12GA for 20A power, but phone service typically should never even reach 1A so 24GA cable is allowed - it's considered low-voltage even though it gets brief spikes of mid-voltage.
BTW, the reason the phone company uses 90V power is that originally the US power grid was also 90V, so the phone company could use the same power generation equipment as the electrical companies. But house voltage has slowly crept up, first to 100, then 110, 115, and now finally 120. I've even seen some places in the US that use 125. THe phone company sticks with 90 anyway.
I did not design this game/I did not name the stakes/I just happen to like apples/And I am not afraid of snakes-AniD
So, anyone have 2 DSL modems working point to point, back to back? Are there any caveats or precautions?
Check out the SDSL / GSDSL Devices from Zyxel; I'm using a lot of these in back-to back configurations covering distances in the range from ~ 300ft to 4 miles.
I'm using two differnt models: the older Prestige 681 SDSL Modems/Routers and newer Prestige 782R G.SHDSL Routers.
Both have a max. linespeed of ~2Mbits; what you actually can get depends both on line quality and distance. Under identical conditions, the newer 782R will get about 20-30% higher troughput.
From my experience I'd expect to get about 1 - 1.5 Mbits over a 2 mile link if it's reasonable quality.
There's probably lots of other devices that would also work, it's just that I've successfully used these myself. Prices (new) in Europe are about $480 each; with a bit of luck you should be able to get them used for a lot less.
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There's enough juice to make you fall off a phone pole or rip your arm up pulling it out of a rack full of Sharp Things. That's what the Telcos don't want.
...and he grinned, like a fox eating shit out of a wire brush.
OdessaOffice.com
This guy lives in rural washington, and had the same problem. This is his complete step-by-step how to on how he did it, including modem brands & models, problems he had while setting it up, how he overcame obstacles, etc. Very very good read and I would think it'd be your first stop for rolling your own.
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I think 90v ac is minimum ring voltage, typical is usualy more like 100v, voltage on-hook is usualy about 48 volts(phone hung up) and drops to about 12V DC when 600 ohms of immpeadance is connected like when you pick up the phone.
as for hooking up DSL modems to a dry pair, i've heard of it being done, just done know how. also the telco may have put a filter on the lines that'll keep dsl from working.
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Quit being retarded!
For about $300 you can get enough wirless equipment to put in a link that will easily go 2 miles, well actualy it will go about 15 miles but that is besides the point.
Anyways I would look at that or this link:
http://www.odessaoffice.com/sdsl.htm
Remember this though. You said in your post that you are to far out from the Telco to get DSL. Okay so how long would thee wire be? You said your friend is close enough to get it..this makes no sense.
Typicaly when the telco runs a line they run it from the Customer Premise to the Telco to the other side of the Customer Premise. Then at the Telco they add what ever service, ie DSL T1 ISDN dialtone, the person is paying for.
What you want is a dry copper pair, also known as a "alarm circuit".
WHAT EVER YOU DO, dont tell them what you are doing. Tell them it is for a alarm to monitor your house or something like that.
Would it be possible to 'daisy chain' the DSL modems to go many miles while maintaining excellent throughput? For example, if the distance causes the bandwitdh to halve, then why not buy 2 extra modems and throw them in the middle as a repeater?
A company I worked for did something like this for some point-to-point connections in Toronto, Canada using dry pairs from Bell Data.
2 problems: we used units from Paradyne which had TREMENDOUS quality control problems - units were always physically dying (either the insert DSL card or the chassis itself).
Secondly, check your SLA's. Bell Canada Data only guaranteed 9600 Baud end-to-end and had a clause that said they only responded within 48 hrs - which meant they took 48 hrs to call you back. Most of our non-Paradyne problems were cause by the line quality - we think at least a couple of our lines were in a conduit that had a leak - every time it rained heavily the circuit died. About a day after it stopped raining, the circuit came back, no intervention, no calls to Bell.
So, yes, it can work, but use decent equipment and make sure your local telco will support you in a timely fashion.