Can ADSL run on a single wire?

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Flidiot

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Strange question, but last week our voice service was completely dead at the office. ADSL was fine though - line was degraded, but usable.

When the techie came out and checked the lines in the office he mentioned that only one wire, of the pair, was still live.

It seemed quite strange to me, so I asked how the ADSL can still be connected if both wires in the pair are not connected - he said that the voice line uses two lines, but ADSL only uses 1?? :confused:

Anyone know anything about this? Maybe have an explanation for how this works? I was under the impression that one would need a full pair to complete the circuit - like a power cable, live and neutral.
 
You need 2 wires at the very least, otherwise you could've like powered your car with only 1 cable being connected on the battery...

Voice & ADSL run over the same pair of wires, and then at the DSLAM (I might be wrong where they separate them) they get separated with a low pass filter for the ADSL signal and a high-pass filter to get the voice signal.
 
Pada said:
You need 2 wires at the very least, otherwise you could've like powered your car with only 1 cable being connected on the battery...

Voice & ADSL run over the same pair of wires, and then at the DSLAM (I might be wrong where they separate them) they get separated with a low pass filter for the ADSL signal and a high-pass filter to get the voice signal.
Click to expand...

I thought it sounded a bit...suspect.

Like I said, I was under the impression that a pair is needed - a single wire sustaining the connection just doesn't make logical sense.

Chances are the dude had his night-cap a little early that day
 
I think that the reason why the ADSL continues to work is because the bad joint which is no longer able to pass DC voltages can still allow AC signals through by acting as a small capacitor. Apparently an ADSL line which has a telephone connected that draws current directly from the line (i.e. no external power source) will require less maintenance than one that only has a router attached. The DC current flow apparently helps to prevent the joints from oxidising.
 
Flidiot said:
I thought it sounded a bit...suspect.

Like I said, I was under the impression that a pair is needed - a single wire sustaining the connection just doesn't make logical sense.

Chances are the dude had his night-cap a little early that day
Click to expand...

You do get 1-wire communication methods, so don't make the mistake of assuming you need a minimum of 2 wires to get things going. The ADSL we use in SA is full-duplex exclusively as far as I know (My knowledge regarding the technologies employed by Telkom is limited) and thus you need a pair to be able to communicate with the exchange.
 
Pada said:
You need 2 wires at the very least, otherwise you could've like powered your car with only 1 cable being connected on the battery...

Voice & ADSL run over the same pair of wires, and then at the DSLAM (I might be wrong where they separate them) they get separated with a low pass filter for the ADSL signal and a high-pass filter to get the voice signal.
Click to expand...

My voice and ADSL runs on separate pairs from my house.

I had an issue where my sync would drop as soon as the phone is picked up no matter I did.

Telkom techie came out to my house to check what the problem was, he also couldn't find the problem so he put in a new splitter box and connected one pair to each of the jacks. Problem sorted and I have a slightly higher SNR margin now as well.

This is apparently only possible on some exchanges though.
 
I've had the pairs replaced twice at my home over the years. My phone disconnected and was weak and the ADSL line would only synch at it's lowest and drop synch totally, the issue for me was the line could not sustain the minumum voltage required to maintain connection.
 
grim said:
My voice and ADSL runs on separate pairs from my house.

I had an issue where my sync would drop as soon as the phone is picked up no matter I did.

Telkom techie came out to my house to check what the problem was, he also couldn't find the problem so he put in a new splitter box and connected one pair to each of the jacks. Problem sorted and I have a slightly higher SNR margin now as well.

This is apparently only possible on some exchanges though.
Click to expand...

Kosmik said:
I've had the pairs replaced twice at my home over the years. My phone disconnected and was weak and the ADSL line would only synch at it's lowest and drop synch totally, the issue for me was the line could not sustain the minumum voltage required to maintain connection.
Click to expand...

In both of these cases though, you still had a full pair to connect, right? I.e. two physical wires connected (Except in Kosmik's case where you had two pairs - one for voice, one for DSL).

We have a single pair (two wires), but according to the tech, only one of the two wires was physically connected. There was apparently a problem at one of the telephone poles about 200m down the road, where one wire had just decided to disconnect?? I stand by my previous assumption, he probably had his night-cap early that day :p
 
bekdik said:
Maybe there's an earth loop providing the second connection, i.e. acting as the second wire?
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Interesting theory... I know for sure that we only have a single pair in the building itself, but the problem wasn't in our building and obviously I did not see what was going on beyond that point.
 
Well, is your ADSL twice as nice with the second wire attached?
 
bin3 said:
Well, is your ADSL twice as nice with the second wire attached?
Click to expand...

Haha, more than twice. The 4MB line was syncing at 1056kbps, SNR etc. actually looked OK (can't remember offhand what it was). Our actual speeds though (across multiple ISP's) were about 20-25kbps down, 4kbps up. After the connection was sorted it came back up to 300 odd down, 25 up. Just called telkom to recreate the line port and we went back up to full 4MB speeds.
 
Flidiot said:
In both of these cases though, you still had a full pair to connect, right? I.e. two physical wires connected (Except in Kosmik's case where you had two pairs - one for voice, one for DSL).

We have a single pair (two wires), but according to the tech, only one of the two wires was physically connected. There was apparently a problem at one of the telephone poles about 200m down the road, where one wire had just decided to disconnect?? I stand by my previous assumption, he probably had his night-cap early that day :p
Click to expand...

I have two pairs(2x2 wires) connected now as well, one for voice and one for ADSL.
 
grim said:
I have two pairs(2x2 wires) connected now as well, one for voice and one for ADSL.
Click to expand...

I spoke to a friend this morning who has actually done the same. What issues were you experiencing? Or did you request that it be connected like that to be pro-active?
 
Flidiot said:
I spoke to a friend this morning who has actually done the same. What issues were you experiencing? Or did you request that it be connected like that to be pro-active?
Click to expand...

The line would loose sync whenever the telephone was picked up no matter what I tried, new filters, different router etc.

The line was fine for years before this started happening.
 
grim said:
The line would loose sync whenever the telephone was picked up no matter what I tried, new filters, different router etc.

The line was fine for years before this started happening.
Click to expand...

Sorry - I actually made you repeat yourself there - you already mentioned previously what was happening, my brain wasn't registering for a second.

I am wondering if this may not be the case at a client of mine out Plumbstead way... Their net is constantly going on and off, I must maybe just ask them to check if it drops when they make/receive calls.
 
Flidiot said:
Strange question, but last week our voice service was completely dead at the office. ADSL was fine though - line was degraded, but usable.

When the techie came out and checked the lines in the office he mentioned that only one wire, of the pair, was still live.

It seemed quite strange to me, so I asked how the ADSL can still be connected if both wires in the pair are not connected - he said that the voice line uses two lines, but ADSL only uses 1?? :confused:

Anyone know anything about this? Maybe have an explanation for how this works? I was under the impression that one would need a full pair to complete the circuit - like a power cable, live and neutral.
Click to expand...

What he said is quite correct it is either transmitting or receiving data so only need one wire to work and all signalling on ADSL is data not like POTS needs a loop to seize the line in the exchange.
The ADSL is wired from the telephone number in the exchange to the DSLAM and then out the DSLAM to the cable pair that goes to the subscriber .Telehone exchange and DSLAM are 2 separate entities.
 
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FNfal said:
What he said is quite correct it is either transmitting or receiving data so only need one wire will work and all signalling on ADSL is data not like POTS needs a loop to seize the line in the exchange.
Click to expand...

That's quite interesting. I was really under the impression that you need a complete loop.

Could the fact that only one wire was connected have an impact on the ADSL performance? Or was is it more likely just a coincidence that the ADSL degraded at the same time?
 
Yes you would get a degraded service because the line is unbalanced (can cause other problems to reflections etc.) and the DSLAM will try to compensate
 
You can run ADSL in SA on a single wire, it works I've experienced this when we had a cable break.
 
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