number of lines on connection box affects adsl spped

Hi, I've just set up new offices where BT have installed 3 lines for us, and are about to install another line for one of the offices rented by another business. I am the landlord.

When they installed the first 3 lines 1 month ago, they used a connenction box like this which they placed in our suspended ceiling:
http://imgur.com/GzfR9
off which the master sockets for our 3 lines go. One of these lines has ADSL2+ on it, with measured speed of about 18Mb download.

Here's what it looks like inside (or was I not allowed to open it - oops):
http://i.imgur.com/dDGiB.jpg

The black wire comes from the outside, I think from a connection box a few shops down. (We are offices above a shop).

Our new tenant asked to share our ADSL connection but we refused because he intends to use VoIP which will affect our bandwidth and download limit, which we sorely need.

So, this tenant has arranged for a new BT line for his own ADSL connection.

Now, no doubt this will be run of this connection box within our suspended ceiling, rather than the engineers running a new cable from the street cabinet or the nearest external box.

So my question is, will this affect our existing ADSL connection on the first line which runs from the same box?

In other words, have we gained nothing by having him create a new ADSL line, rather than sharing our own.

Or is it that Bt will have take into account the contention ratio and anyway we would have 20 lines sharing our DSLAM or whatever in the exchange and so an extra line, even if run of the same connection box, makes no difference?

The number of lines won't affect the available bandwidth as each line will have it's own connection to Bt Wholesale kit or the LLU kit of the isp they choose
But there can sometimes be cross talk, electromagnetic leakage within the cable bundles, But the set up you have shown, should not give any problems,normally

In reply to a post by tommy45:

The number of lines won't affect the available bandwidth as each line will have it's own connection to Bt Wholesale kit or the LLU kit of the isp they choose

OK, so although they share this black cable to outside the building (which through another box eventually reaches our nearest cabinet 200 yards away) this won't affect the bandwidth of the existing line, right?

The "connection to the bt wholesale kit" (this isn't LLU) happens at the exchance, correct?

many thanks!

In reply to a post by ashirusnw:

In reply to a post by tommy45:

The number of lines won't affect the available bandwidth as each line will have it's own connection to Bt Wholesale kit or the LLU kit of the isp they choose

OK, so although they share this black cable to outside the building (which through another box eventually reaches our nearest cabinet 200 yards away) this won't affect the bandwidth of the existing line, right?

The "connection to the bt wholesale kit" (this isn't LLU) happens at the exchange, correct?

many thanks!

It's quite likely that the new line will involve a new cable from the junction box outside( on the wall &Grey in colour) into the property, as you are already using 3 pairs from the existing cable, (not sure how many they have )
But each line is connected separately to the ISP's kit at the exchange should ADSL be required, so each line will work independently including available bandwidth,

That's probably a 5-pair cable, so there's a fair chance it will be taken from the box you have pictured.

As mentioned above, there may be a *marginal* difference to the sync speed due to crosstalk between pairs on the cable, but I doubt that you would ever notice any real difference.

It looks like a 5-pair cable to me too, as we have a very similar box mounted on the wall in our boiler-house at work. This has a 10-pair drop wire, which is quite a bit larger than the one in your picture.

Like you, there are two businesses that run from this site. BT have always just used the 10-pair to add new lines for either business. Our phone service is over SDH via underground fibre, so there's plenty of pairs left for the other tenant.

This boiler-house is accessible from the outside at all times. BT won't set things up so they'd need access to one office in order to provide new lines in another. Therefore, in your case, they might reserve those spare pairs for future expansion of your service and install another drop wire to your tenant.