What Exactly is a Carrier Line?

Altreab

We have been talking about carrier lines and know that it stops you having BB if its on your line. Now can anyone please tell me exactly how it works?
My present understanding is that say 5 people have their calls transmitted through a single copper line. This is done by allocating different frequencies to each dialed number? Am i correct or WAY off the mark?
How many carrier lines can be put on a single strand of copper? What can anyone tell me is the average amount of users per shared copper line in the West?

kaizersoze

I'm not too sure of the mechanics of it myself but, according to a retired Eircom engineer friend, up to 4 users could be put on a carrier. He said that 2 or 3 users was the norm. He retired about 5 years ago and that was the practice up to then.

Sponge Bob

up to 16 on a line with some of the more 'modern' ones.

its cheaper than running copper .

po0k

DACS/Pairgain/Split line I assume?

Altreab

SyxPak wrote:

DACS/Pairgain/Split line I assume?

Yes .... anywhere i can find the technical info on how it works?

lucernarian

I think they are made by Tadiran Telecommunications, an Israeli company. There is virtually no information about the devices on their website. You can find out a lot more about the BT DACS systems on the internet. They use something very similar to an ISDN line to provide 2 phone lines to people, using one copper pair.

gerryo

The one outside my house has 4 ports (only one connected).

I seem to remember hearing a frequency of 500KHz mentioned, can't really remember who said that. I believe each port has up to 32Kb/S bandwidth, probably ADPCM.

Since I cannot connect higher than 31.2Kb/S, that seems to tally.
However, as there is only one port in use, the BW might be shared, if so, that might explain why there are people with 9.6Kb/S connections.

Power is supplied by the exchange, phantomed over the copper.
The box has on/off hook detection, generates ringing voltage locally.

They are a hangover from the days when copper lines were scarce & since only a voice quality line is guaranteed from Eircom, they were considered an acceptable compromise.

If you are connected to one of these, you cannot get any form of broadband.

byte

Do Eircom still actively use these for new line connections?

TimTim

byte wrote:

Do Eircom still actively use these for new line connections?

As far as I know they aren't suppoused to but this is eircom after all.....

watty

Long ago especially trunks used "carriers" the available bandwidth was split into 4kHz chunks and it was like Channelised SSB radio over pair, or even over a coax (which allowed 100s of channels).

PCM /TDM made it obsolete for trunks.

each ISDN channel is what lives on the PCM 31 +1 channel TDM (the 32nd has all the signalling. giving 2.048 Mbps. That system is now obsolete too).

Some "carrier" systems long ago may have been SSB analog, but nowadays more likey a cut down ISDN/TDM with more than 2 channels and less than 32.

These not able to support 56K modems or Broadband.

cgarvey

TimTim wrote:

As far as I know they aren't suppoused to but this is eircom after all.....

Was that not dismissed as an urban myth? Was it not "where possible, blah blah" (which in practice makes no difference whatsoever, because eircom need only say "but there's no copper left, and it's not viable to lay new trunking")?

kaizersoze

cgarvey wrote:

Was that not dismissed as an urban myth? Was it not "where possible, blah blah" (which in practice makes no difference whatsoever, because eircom need only say "but there's no copper left, and it's not viable to lay new trunking")?

GarfieldConnoll posted in the Smart BB thread some time ago that they received a "assurance" from Eircom that "new lines would not be served using carriers" (whatever thats worth). You're right of course. The old "where possible" proviso will be quoted by Eircom at every opportunity.

lucernarian

For all they are worth in Ireland, Remote Subscriber Units, AKA sub-exchanges are a new version of pairgain. On a large scale.

Instead of eircom shelling out thousands on a 400-pair cable to a new estate on the outskirts of a town, with the recent prices of copper and all, they lay a fibre cable to a cabinet, virtually identical in appearance to the ubiquitous green ones across Ireland. They install a miniature exchange, usually with its own 4 digit number range in this. DSL? Fat chance.

Instead of multiplexing lines remotely with a copper pair, they are doing it with fibre. I haven't yet heard of an RSU with DSL enabled. Telstra in Australia are slowly removing these devices and replacing them with DSLAMs installed in them.

It will be truly ironic if eircom continue this absurd practice, with their new Aussie owners:rolleyes:

Sponge Bob

To_be_confirmed wrote:

For all they are worth in Ireland, Remote Subscriber Units, AKA sub-exchanges are a new version of pairgain. On a large scale.

and a jolly decent technology it is if used properly !

Instead of eircom shelling out thousands on a 400-pair cable to a new estate on the outskirts of a town, with the recent prices of copper and all, they lay a fibre cable to a cabinet, virtually identical in appearance to the ubiquitous green ones across Ireland. They install a miniature exchange, usually with its own 4 digit number range in this.

correct, the cost of a 50pair (never mind 400) is €10000 a KM nowadays . Copper economics are pretty brutal

DSL? Fat chance.

There are two reasons for this.

1. EIRCOM CABINETS ARE NORMALLY A WRONG DESIGN AND HAVE NO SPACE FOR DSL GEAR
2. Technically these are new exchanges and as 400 houses = 1000 people eircom deem the exchange to be "too small "

But its academic, they need to put another cab out there beside the first one to support DSL , and they won't.

I haven't yet heard of an RSU with DSL enabled. Telstra in Australia are slowly removing these devices and replacing them with DSLAMs installed in them.

They are called RIMs in Australia and are quite a different design to ours, being mounted on legs to keep the termites out

I have heard of these telephone+dsl cabinets being installed with DSL in Ireland. It happened once I for a high density dublin development like adamstown .

It will be truly ironic if eircom continue this absurd practice, with their new Aussie owners:rolleyes:

Ironic my arse, they have another 100 of these DSL less cabinets in a warehouse and will use all of them.

Once they run out they may order a new model with a DSL shelf in it , stranger things have happened.

lucernarian

Sweet Jesus..... 100 cabinets... I presume these cabinets were ordered by eircom knowing full well they could not install DSL cards?

Actually, are they the exact same as the copper-only cabinets except crammed with fibre PSTN switches? Or is the cabinet housing a tad more sophisticated?:p

icom

http://en.wikipedia.org/wiki/Pair_gain

damien

kaizersoze wrote:

GarfieldConnoll posted in the Smart BB thread some time ago that they received a "assurance" from Eircom that "new lines would not be served using carriers" (whatever thats worth). You're right of course. The old "where possible" proviso will be quoted by Eircom at every opportunity.

That's bull. Maybe this was the same conversation where they assured Smart they'd help them as much as possible with LLU and number portability was working. How's them for apples?

ComReg told us new estates are getting pair gains so I think the possibilty is quite high.

Sponge Bob

the 'assurance' is in the public domain and is called the CLFMP

http://www.eircomwholesale.ie/dynamic/pdf/LLU%20IPM.pdf

and

http://www.eircomwholesale.ie/dynamic/pdf/clfmp_iss3.pdf#search=%22eircomwholesale.ie%3A%20clfmp%22

and

http://www.boards.ie/vbulletin/archive/index.php/t-230573.html

Altreab

Sponge Bob wrote:

correct, the cost of a 50pair (never mind 400) is €10000 a KM nowadays . Copper economics are pretty brutal
.

What speed would Fibre costing the same deliver?
i guess it would make too much sense just to have fibre connecting every exchange and mini exchange in the country!! Sell the copper thats there now and replace it with Fibre.

watty

I dunno. One fiber might be able to do 200Gbps these days, you would stick a bunch in for not much more cost.
I can't imagine why anyone would stick copper anyplace any more. Except for final from kerb to house. Coax or Cat 5 then. Some applications coax is more usefull than twisted pair. But it is expensive stuff.