I originally put this page together in the days of dial-up modems and life has moved on considerably. Broadband is now commonplace and I have enjoyed the always-on high-speed access it provides since 2002. However, I am aware that not everyone has broadband and may still be soldiering on with a squawking dial-up modem.
We all take our internet connection for granted these days but should we? I had to learn about the subject after finding myself with an impossibly slow connection. I first suffered in 1998 in Bedfordshire and then suffered again after moving house to Derbyshire a couple of years later.
The previous owners of my house in Bedfordshire had had two telephone lines rented from BT and I only wanted one. So BT did their usual trick of pulling the connections at the exchange and the second socket was dead. Only it wasn’t silent, if I plugged a phone in I heard a high-pitched buzzing. There was a large white box screwed to the wall next to the second socket with the letters DACS and BT moulded into the cover and this box wasn’t dead either, occasionally I would hear it go into a frenzy of clicking for a few seconds. I asked BT about it and they told me not to worry, it wouldn’t do any harm and they didn’t need it back.
Then I started to enquire about my DACS box and found out what it was and how it worked. The DACS or Digital Access Carrier System combines two analogue (normal) signals into one digital signal so that two customers share the same line from the exchange. It is a form of modem (MOdulator-DEModulator) and it can take many guises. It can be inside your house if you have two lines. If you only have the one, it can sit at the top of a pole or even be underground. It is the modern form of a Party Line except that both customers can use the line at the same time without knowing the other is there. Only they do share the bandwidth, which means that each party only gets half what they might get if they had the line to themselves.
This was no problem at all when modem speeds were struggling along at 9,600 bps or 14,400 bps, even a 28,800 bps modem managed perfectly well. But when 33k and V90 came along, the problems started. They would continue to work (most of the time) but you could never achieve better than about 31 kbps, that was the finite limit even for a good line, a short distance from the exchange. A line longer than a couple of miles would struggle to achieve 28k. Sometimes I could get no connection at all, most ISPs in the UK won’t accept a connection slower than 28k because it wastes their available bandwidth. All the helpdesk people I called suggested resetting this and that and I even reinstalled Windows to try and improve things, but all was in vain.
As soon as I found out what my DACS box was doing, I called BT and insisted that they removed their kit immediately. Well, they did and I immediately enjoyed connection speeds of 33 kbps, 36 kbps and even higher. Joy!
The point was proved beyond any doubt after ntl arrived in Bedfordshire. I took a subscription for cable TV and a new telephone line with an ISP account with ntlWorld. The internet connection was very fast and I regularly enjoyed connection speeds in the range of 41 kbps.
That all changed when I moved to Derbyshire and I found I was struggling to get 31k or even 28k. I did all the usual checks and even remade all the telephone line joints inside the house. Then I remembered my earlier experiences with DACS and had a look around. There is a distribution pole right outside my house with four boxes at the top as you can see in the picture on the right. The big one on the left is the main distribution connection box from the incoming cable and I wondered if the others were DACS boxes. So I phoned BT’s helpdesk to ask if I was on a shared line. “No.” was the answer.
I rephrased the question: “Am I connected via a DACS box?” “Just a minute.” ... and I was put on hold for nearly five minutes. Then she came back: “Yes.”
So I explained the difficulties I was having and asked to be given a direct line connection to the exchange. She refused outright and went into a long explanation of my “rights” and that the European Telephone Charter only entitled me to an analogue connection of 9,600 bps, although they “tried to do better”. Funny how Europe gets the blame for everything these days! It’s a convenient excuse to hide behind.
To cut a very long story short, I wrote a letter to OFCOM (they were called OFTEL then) to explain my difficulties and suggesting that BT were taking advantage of their monopoly position since no other cable operator had any likelihood of arriving in my part of the county for several years. They wrote back and sympathised with my position, reiterated the European Telephone Charter and said they would write to BT to ask them to reconsider. I assumed that was the end of the road and that I would have to put up with a lousy connection which I could make only very limited use of.
And then, out of the blue, a couple of BT technicians arrived at our front door one morning and said they were reconnecting us! They spent about half an hour at the top of the pole and went away again after checking that our phone was working OK. And that evening, I found that I connected at 38 kbps, just like that! They had reconnected the lines at the top of the pole and some other poor soul in my street is now connected via a DACS box. I only hope they don’t have an internet connection!
So maybe modems only really work on a wing and a prayer?
But as of 25th July 2003, BT (and Hull’s Kingston Communications) are required by OFCOM Regulation to supply a line capable of supporting dial-up net access at a speed of at least 28.8 kbps. Any customers who cannot connect at this speed have grounds for a complaint and BT and Kingston must make reasonable efforts to improve the service. So nobody will be forced to suffer a DACS box on a dial-up connection any more.
Broadband arrived on my exchange in August 2002 so I applied for a “wires only” connection, an option then available at a reduced price. I bought an ADSL-SAR310 PCI card and a Microfilter from Solwise which arrived in the post the day after and I installed it in readiness. I was connected on Monday 2nd September 2002, two days earlier than BT promised and I immediately enjoyed speeds of 576 kbps down and 288 kbps up. Wow!
Then in March 2003 I installed an ADSL-SAR715 modem router, again from Solwise, so that I could share the connection by networking two computers together. That performed perfectly well until the autumn of 2005 when my connection began to slow down and become unavailable at times. I eventually realised that the modem was not holding its settings and appeared to have reached the end of its useful life. So in December I cut my losses and chose a new modem router, this time a Netgear Firewall Router model DG834. The installation for this could not have been more different from the Solwise which, as I read in a magazine review later, was about the most difficult device to set up they had ever come across. In retrospect, it’s a wonder I ever got it work! The Netgear was perfect simplicity to install and set up, it was fully automatic and got it right first time. And it’s fast, my downlink speed is 2.2 Mbps! Highly recommended.
* February 2008 – the Netgear modem started to die and I had to replace it. This time I have gone for a Sitecom ADSL 2+ Modem Router because that’s what my local branch of Maplin had in stock when I called in. It seems that modems have a design life of 26 months or so and then they die! Interestingly, each modem has been roughly half the physical size of the previous model and somewhat lighter in weight. The continuing march of miniaturisation.
* For further reading on telephone exchanges and how they work, try this site which has a lot of information about the whole subject of the telephone service in general. It used to have a page on shared service lines but this has disappeared. I have a cached copy available here.
This page last updated 9th November 2008 © J S Rastall.
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