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DACS FAQ


What does DACS stand for?

Digital Access Carrier System

What does DACS do?

It allows two ordinary phone lines to be stuffed down a single telephone line. DACS doubles subscriber capacity of twisted copper pairs.

Why BT want to do that?

You, or one of your neighbours, asked for an additional line be installed. There wasn't a spare line going to the telephone exchange.

Installing a DACS is quicker and not so expensive as running in a new telephone cable all the way back to the exchange.

Why would BT not be able to find a spare pair?

More and more people are requesting additional lines, usually for internet access.

Why aren't they any good for Broadband?

They are fine for modems up to 33.6kbps and fax machines, and fine for voice.

Broadband ADSL only works on a normal copper pair that is continuous from your house to the exchange. A DACS breaks this continuous connection.

How does DACS work?

They incorporate high speed (up to 160 Kbit/sec) digital transmission and echo cancellation techniques and use ISDN (Integrated Services Digital Network) protocols.

Is it likely that I have one?

"ECI has already supplied in excess of 100,000 systems to BT" by 1996. The equipment near the customer premises is enclosed in a small plastic box 20cm by 10 cm by 40cm, small enough to be hidden underground with the distribution point underground. The exchange end is rack mounted.

You have a DACS if the BT Broadband Availability checker reports:

"Note: Our records indicate that a line-sharing device is connected to your line. This is the reason that the checker has returned this marginal result and may mean that Broadband could not be delivered on this line. Further investigations would be necessary as part of the ordering process to confirm whether or not you could receive Broadband service at this address. This could result in a delay to the provision of broadband at this address."
 

Is there anything good about being DACSed?

If your dial-up speed was very slow you may now get 33.6kbps. (And BT can install DACS a lot faster than running in a cable.)

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