DACS
dsl will not work through a dacs either through an exchange unit (although why on earth anyone would jumper a dsl and still have it going through a eu dacs. It's not a mistake any one could make). or through a remote unit.
To provide dsl on a line which is on a dacs means it will have to be de-dacs'ed.
Just to explain what a dacs is, it referd to as a "pair gain device". In circumstanses where ther are not enough pairs of wires in the network to get all the working lines in demand for a route a dacs digitaly encodes 2 lines at the exchange via the exchange unit (EU) and sends this signal down the same pair of wires. this is then decoded by the remote unit (RU) at a reasonable point near the 2 customers for the 2 lines which then feeds off to the relavent nte's as with a normal line.
The technology pre-dates dsl so wasn't designed to allow the dsl signal to pass through it.
The only way an end user might know if a line was running via a dacs is on normal dial-up internet the speed peaks at 28kbps.
The problem with de-dacs-ing a line is that the dacs is on there for a good reason, so we need to find another good pair from the exchange to the ru to put the line on. Unless there's either only one working line on that dacs (then the dacs can be removed completely) or if there's another line by the ru which isn't dsl, isdn, or has regular digital traffic which can be swapped with the number your trying to de-dacs. then the job can become a nightmare.
If an engineer gets a tack on their laptop with the description de-dacs and with out the 2 easyer options, they usually cringe throw a hissy fit, use a few words not to be repeated in front of their mother etc etc.
They normaly tend to be found at the end of long routes in the country side or some times in very high density of line areas like shopping roads/streets. It's a black box slightly narrower than a dp as found as the top of poles a give away is a 30mm white square at the bottom right of the face of the ru, internal ru are in all white, on an incomming call you can hear it clicking inside as it generates the ring.
Thanks to dsl having both internet and normal voice telephony running on the same pair this has feed up a lot of demand for pairs where end users had a second dedicated line for their internet connection in the past.
One delevopment of dacs was know as Homehighway isdn, here you have 2 64kbps isdn channels down the same line, one can be voice one internet, when not using the voice connection the 2 64k channels combine to give a 128k connection, this is defined in europe as mid band. the most parts of the US this would you belive is called broadband ! I think in 1994 there where more 512+ lines working in the old 9 nations of the eec than in the whole of the usa.
