Controlling multiple base stations over telco dry pairs

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adlertom
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Controlling multiple base stations over telco dry pairs

Post by adlertom »

I have three base stations at a remote location, tone controlled via three leased telephone company "dry pairs". Some of you may recall a post I made last year when I was first setting this up:

http://batboard.batlabs.com/viewtopic.p ... 66#p394875

At that time, I decided to go with a separate leased line for each of the three stations. The leased lines are actual dry pairs i.e. they simply pass through the telco central office, without going through any switching equipment. For a while I was even doing DC control with one of the pairs!

Fast forward to today - now I'm looking at adding another station. I could of course lease another dry pair. However I'm wondering if I could somehow multiplex several tone control signals over one of the pairs. Could I perhaps do the same thing that the telephone company does with T1 circuits, since I have access to the full bandwidth capability of the copper pair?

I't about 6/10 of a mile line of sight between the control point and the remote location. I'm guessing it's no more than 1.5 to 2 miles total copper run through the CO, by the time it makes all the twist and turns between the two points.
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

For the cost of the three leased lines, you should look into changing over to one dsl to the site. Then you could do roip to as many radios as you want.
adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

Bill,

Would DSL play nice with analog tone control? I don't want the keying tones to get (to borrow your word from last year's discussion) "farbled".

Tom
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

That is a danger. I know NXU's do not faithfully maintain tone quality. Some guys have stated they have good luck passing tone control over ip with other products. We'd have to find some of the other threads to see what they were using. OTOH, if you can switch over to hardware (aka local) control, you can use the E&M keying in NXU with great reliability.

OR, you can go through the expense of an IP223 at each end. At the control point it would interpret the tone control, encode the command on ip, and regenerate it at the base station. Each IP223 can control two base stations. So, you would need four for this project.

Found this - Tone control over IP - tpg talks about using the RAD IP-Mux-1E with good success transporting tone control.
adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

All of these devices appear to be designed to transport audio over a WAN, which I don't have available to me between the two sites. All I have are 6 copper wires (3 dry pairs) to work with.

I was hoping there would be some product available that could frequency division multiplex an analog line. Something like using 0-3000 Hz of bandwidth for voice path 1, 3000-6000 Hz for voice path 2, 6000-9000 Hz for voice path 3, etc.

The magical device I seek would shift the audio up in frequency on one end and back down on the other. Since my telco circuits are dry pairs, with no "processing" by the phone company in between, I wouldn't be limited to the 300-3000 Hz bandwidth of a typical switched telco circuit.
adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

Here's another idea. Would this work?

Instead of the current use of two wires for each circuit:

--------> L1 +
--------> L1 -
--------> L2 +
--------> L2 -
--------> L3 +
--------> L3 -


Use one wire for common - and the other wires for +:


--------> common -
--------> L1 +
--------> L2 +
--------> L3 +
--------> L4 +
--------> L5 +

The closest real world example I can think of would be a stereo audio plug, where three wires are used to convey two audio paths.
RFguy
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Re: Controlling multiple base stations over telco dry pairs

Post by RFguy »

adlertom wrote:Here's another idea. Would this work?

Instead of the current use of two wires for each circuit:

--------> L1 +
--------> L1 -
--------> L2 +
--------> L2 -
--------> L3 +
--------> L3 -


Use one wire for common - and the other wires for +:


--------> common -
--------> L1 +
--------> L2 +
--------> L3 +
--------> L4 +
--------> L5 +

The closest real world example I can think of would be a stereo audio plug, where three wires are used to convey two audio paths.
Yes, theoretically it would work if the equipment was all in one room, but lease lines are balanced pairs. Running unbalanced will result in hum and noise.
adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

Good point. I hadn't considered that the new scheme would be unbalanced.
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wavetar
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Re: Controlling multiple base stations over telco dry pairs

Post by wavetar »

If they're truly 'dry pairs' as you state, would they be balanced? Wouldn't that mean they are running through ancillary telco equipment, which you didn't seem to think they were?
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adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

wavetar wrote:If they're truly 'dry pairs' as you state, would they be balanced? Wouldn't that mean they are running through ancillary telco equipment, which you didn't seem to think they were?
They are truly dry pairs. I think they would still be balanced - balancing would not require them to run through any ancillary equipment.

A balanced pair running over a distance picks up induced noise equally on both wires, thus the noise influences cancel each other out. So, as RFGuy pointed out, if I tried to get "double duty" out of one of the wires, the sine wave voltage on that wire would be overall higher than the other one, and therefore there would be no noise cancellation.

What I'm having a hard time finding out is how the phone company did frequency-division-multiplexing in the "old days" before everything went digital. If I could keep signal A at 300-3000 Hz, and up-convert signal B at 3300-6000 Hz at one end, and then separate out and down-convert signal B back down to 0-3000 Hz at the other end, I think that would be a solution.

Any old phone guys out there?
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xmo
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Re: Controlling multiple base stations over telco dry pairs

Post by xmo »

AML

AML stands for Added Main Line.

AML is technology used to piggyback a second voice line on an existing pair of copper wires serving an existing voice line.
MassFD
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Re: Controlling multiple base stations over telco dry pairs

Post by MassFD »

Do not count on a Telco dry pair handling anything over 3000hz so forget the up converting idea. Most RT circuits I have delt with you felt lucky to get 300 to 3000 without a 3db drop off at either the high or low freq
Cause Motorola said so that's why
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Re: Controlling multiple base stations over telco dry pairs

Post by techie »

With the right parts, you could use two of the pairs to create a third "phantom circuit".

You would need 2 pairs of center tapped repeat coils (transformers to the rest of us).
Tellabs 4421/4422 or 4424/4425, Wescom 730, or Western Electric types.
I know WE 111C's will work, but they are probably overkill.
They want to be 600:600CT.

The 4421 and 4424 are single repeat coil modules, and 4422 and 4425 are dual.
4424/4425 are 15khz. I don't know what the specs on the 4421/4422 are..
All of these would have to come from the used market.. don't get gouged..

CT side goes towards the telco, non-CT side goes towards your equipment.
line 1 goes to the first repeat coil, line 2 goes to the second, and line 3 goes to the CT's.

http://en.wikipedia.org/wiki/Phantom_circuit
http://www.kadiak.org/tel/17-3.htm
http://www.telephonecollectors.org/sing ... hantom.htm
http://www.kadiak.org/tel/tellabs/
http://www.kadiak.org/tel/wescom/
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

xmo wrote:AML

AML stands for Added Main Line.

AML is technology used to piggyback a second voice line on an existing pair of copper wires serving an existing voice line.
DAML (digital added main line) is essentially frac T1 service limited to 56k total. It wasn't widely implemented. His phone company may not offer the service. I don't think there are consumer grade modems available. Even if he could find some modems to build his own loop through his existing leased lines, I think his tone control would suffer from the sub-rated encoding. He probably would not be able to establish a link on his own since the lines are so long. They exceed the standard LBO, and they have no in-line amplifiers.

I think he going to have to bite the bullet, and either order another leased line to support his legacy tone control equipment, or convert his system to roip through dsl and work out the details. If he has line of sight, he could try a wi-fi link and save all of his telco costs. That would still require conversion to roip, and selecting hardware that performs to his spec. tpg said he has had good luck using the RAD IPMux-1E. It has four analog phone lines, and it may pass his tone control perfectly.
adlertom
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Re: Controlling multiple base stations over telco dry pairs

Post by adlertom »

techie wrote:With the right parts, you could use two of the pairs to create a third "phantom circuit".

That's pretty freaking cool.

The AML is also intriguing. I couldn't find any such equipment currently being marketed in our modern digital world however.

Thanks guys! I'll let you know what I end up doing.
techie
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Re: Controlling multiple base stations over telco dry pairs

Post by techie »

If you have line of sight, rather than converting to ROIP over wifi, I would look at using some of the Adtran Tracer microwave bridges.
These are license free 2.4 or 5.8Ghz radios, with advertised ranges out to about 20-30 miles.
Current products have capacities ranging from mixed 8xT1/16Mbs, up to DS3.

Older products did 2xT1, mixed 4XT1/6Mbs, etc.

I find listings for refurbished 2xT1 radios for ~$600/ea. Add a pair of 2.4Ghz antennas, and a T1 channel bank at each end, and you have 24 DS0 channels, and a spare T1.
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Will
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Re: Controlling multiple base stations over telco dry pairs

Post by Will »

techie wrote:If you have line of sight, rather than converting to ROIP over wifi, I would look at using some of the Adtran Tracer microwave bridges.
These are license free 2.4 or 5.8Ghz radios, with advertised ranges out to about 20-30 miles.
Current products have capacities ranging from mixed 8xT1/16Mbs, up to DS3.

Older products did 2xT1, mixed 4XT1/6Mbs, etc.

I find listings for refurbished 2xT1 radios for ~$600/ea. Add a pair of 2.4Ghz antennas, and a T1 channel bank at each end, and you have 24 DS0 channels, and a spare T1.
And you do not have to pay the telco and worry about line failures.
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

But, he would need a mux.
kj4bnd
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Re: Controlling multiple base stations over telco dry pairs

Post by kj4bnd »

Im glad i saw this..

I have a site that i do not have line of site to.. and 5-6 miles of copper between the main site and the remote.(When they finally install it)

I was thinking of having the phone company give me a 4 wire circuit... (2 radios) however was thinking of just connecting some channel banks on each end. Im sure i could put some mux equip in, or something... this is a grey area for me but it should work right?
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mr.syntrx
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Re: Controlling multiple base stations over telco dry pairs

Post by mr.syntrx »

Old thread but... T1 over SHDSL? Cheap to do using second hand Cisco gear, requires one dry pair.

http://www.cisco.com/en/US/docs/ios/12_ ... #wp1139187
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alex
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Re: Controlling multiple base stations over telco dry pairs

Post by alex »

I've been waiting to find another Cisco CEOIP card to try circuit emulation over IP with two channel banks to see how well it performs using 2 2600XM boxes.

I've also looked in to using the E&M cards - but they seem to only want to support local control of a radio on each end - not a radio on one end and a console using strict tone signaling. I've talked with a couple of the Cisco guys at IWCE and they indicated that it was possible to do but when I contacted them to get some configuration examples they were not extremely helpful.

Like usual the problem with using the internet is always what is between both end points. If they are the same ISP you probably will be much better off than mixing and matching to the point where you will probably get their advertised speeds consistently between endpoints.

Alex
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

mr.syntrx wrote:Old thread but... T1 over SHDSL? Cheap to do using second hand Cisco gear, requires one dry pair.

http://www.cisco.com/en/US/docs/ios/12_ ... #wp1139187
I have never bothered to try. Are you saying two dsl modems will sync up over a dry pair?
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mr.syntrx
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Re: Controlling multiple base stations over telco dry pairs

Post by mr.syntrx »

ADSL modems, commonly known simply as DSL and used for residential internet services won't. SHDSL modems will, up to 4 miles or so if line quality is decent.

Otherwise, there's a box that does this with less configuration:
http://www.rad-direct.com/Product-G-SHD ... SMi-52.htm
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Bill_G
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Re: Controlling multiple base stations over telco dry pairs

Post by Bill_G »

Right on. A pair of dsl modems if all you want is to extend ethernet 20000ft, or the RAD boxes if you want T1 as well. Nice trick. Probably wouldn't work over aldertom's leased lines, but I can think of applications I have.
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Re: Controlling multiple base stations over telco dry pairs

Post by desperado »

geeze.. it's not that hard if you think about it.

you have 3 lines right now. you use 2 of them for audio
set one goes as is the the busiest base station.
set two goes to the other two stations and set 3 controls which station is being controlled at any given time.

Only caveat to it is you will loose the ability to receive from both stations at the same time.
Deal with that via control station receivers.

do a tone remote channel change on the 3rd set of lines to control the switching between the 3 other stations.
short of that.. put the base stations in standard repeater mode and control them via control stations

That would eliminate the need for ANY leased lines and is easily expandable.
By the time you get all the needed hardware to mux the lines you have, if it's even available, you will have spent enough to buy control stations anyhow.
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maxjam
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Re: Controlling multiple base stations over telco dry pairs

Post by maxjam »

Since the Cisco and E&M solution was brought up I updated the configs on my Cisco 2600XM/E&M project I started in 2010.

http://batboard.batlabs.com/viewtopic.p ... 53#p440453

I now have three endpoints including one out of state. It has been working very well for the consolette that I have on the local amateur repeaters.
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