BT warned its broadband resellers that the costs of DIY-broadband will be higher than first thought, as phone lines will have to be protected from the interference DIY broadband connections will cause.
Self-install Aysmmetric Digital Subscriber Line (ADSL) is scheduled to launch next January following trials due to start 3 December.
It will cost half as much to install, as getting a BT engineer to install it, and may be as much as £5 cheaper in monthly rental costs, fuelling hopes that it may give broadband adoption in Britain a badly needed boost.
But users will have to install extra filters to protect each of their phone line extensions from suffering interference, claims BT.
The cost, around £10 per filter, would add up to an extra £30 for consumers with two extra phone lines and a fax machine.
A potential supply shortage of the filters, for which there is currently only one approved supplier, could also cause problems for the trials.
Currently, BT engineers install a faceplate on the socket when connecting users to ADSL, which contains a multi-filter that protects each extension in the home.
But BT's self-installed product will not include the faceplate as it is thought too complicated for users to install.
Instead, BT is using a micro-filter in a two-way jack, that the user plugs into each socket. Each device using a phone line will require one of the filters.
ISPs believe there may be four-week wait for the filters.
"Price is an issue, but the biggest cause for concern is the supply," said Iain Ogilvie, marketing manager at ISP Nildram. "Whether they'll be enough filters for the trial, I'm not sure."
Ian Buckley, marketing manager at business ISP Zen Internet, thought the extra cost was cause for concern.
"We've yet to see the model for the micro-filters and see how much they cost in bulk, but I am worried about the extra cost for consumers."
Nildram's Ogilvie said that the extra cost will not put people off.
"We're still at the early adoption stage. There are two issues with wires-only services we got from customer enquiries. One is reduction in price, but the other is the customer wishing to maintain control over their hardware."
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