The question is really moot, as we don't have the local infrastructure for the service, due to Telkrap's technology decisions. For an example of this issue, here's an article concerning the BT and Deutsche Telekom's offerings from http://www.vnunet.com/news/1107146 :
<b><i>BT says ADSL over ISDN is 'impossible'</b>
BT's asynchronous digital subscriber line will be sold in the UK requiring new lines at an extra cost to customers, despite the fact that its German rival Deutsche Telekom is offering the same service over existing ISDN lines.
BT's asynchronous digital subscriber line (ADSL) will be sold in the UK requiring new lines at an extra cost to customers, despite the fact that its German rival Deutsche Telekom is offering the same service over existing ISDN lines.
BT claims that the two services operate on overlapping frequency spectrums which prevent their concurrent use of the same copper telephone wire pair. Companies will therefore be required to pay for new connections.
But Deutsche Telekom has been offering ADSL alongside ISDN dial-up services on the same copper line pair for more than a year.
Chris Gibbs, BT's head of broadband services, said: "You cannot run this with an ISDN line. If you want ADSL, the only way you can have it is over a PSTN [analogue] line. This is because of the way ISDN is constructed."
"There are frequency clashes, because ISDN effectively uses a higher frequency spectrum. You cannot run ISDN and ADSL at the same time," he stated.
AVM, however, a leading German manufacturer of DSL interfaces, has refuted BT's claim. Kai Allais, international sales director at the company, said: "That is absolutely not true. You can run ISDN and ADSL over the same pair. The Deutsche Telekom service is always over the same pair."
The frequency levels of the two services are configurable by the operator, so it is the operator's decision as to whether any two services overlap, Allais added. "ADSL is a transmission-oriented technology; it is simply a decision of where you split the frequency spectrum between the services," he said.
Tim Johnson, principal telecoms analyst at Ovum, said: "With Deutsche Telekom you have to have ISDN to have ADSL. The trouble lies in the variations between the ADSL standards needed to run alongside ISDN and on conventional telephone lines. The concern is that if you offer ISDN and ADSL on some lines in a bundle, and PSTN and ADSL on others, there is some risk of cross-interference between the separate lines rather than between the two services on the same pair."
BT's stance on this will come as an unpleasant surprise to businesses expecting to use their ISDN lines for concurrent ISDN and ADSL services. Doing so would allow them to retain their ISDN facilities for fast dial-up connections when necessary.
"In Germany they use a different frequency to the UK, and we are also aware of a number of interference problems our customers would wish to avoid," said a BT spokesman.
BT is already taking orders for business and domestic ADSL services, and early installations are expected this summer.</i>
can be on the net and phone at the same time without effecting the speed. I just hope I can use my current phone line for ADSL, since when I used it for internet years ago the fastest I got was 14400bps, but there website did say that my exchange supported ADSL.