Telecommunications repair crews in Canberra are struggling to keep ahead of fires threatening to bear down again on the city as authorities warn residents of the capital's north to prepare for the worst.

A Telstra spokesperson said the telecommunications heavyweight expected the number of residents without service to remain stable for the time being, despite the arrival of interstate repair crews in Canberra to assist beleaguered local staff.

There are around 360 Telstra workers in Canberra -- mostly cable layers and joiners -- but the carrier said 20 to 30 of those had returned home to protect their own properties.

"A lot [of services] have been restored, there was about 4,500 [services down] and we expect about the same today, as some have been fixed, more have come in," said Tim Scott, Telstra corporate affairs manager for NSW.

Scott said that, in some cases service would be restored within days, while in others it was expected to take a week. Service restoration work in the hardest-hit suburb, Duffy, is not expected to start until Thursday.

Broadband and cable television provider TransACT is presenting a slightly more positive picture, but as at midday Tuesday it also faced uncertainty as the fires threatened to approach from the city's north. A TransACT spokesperson said the company had managed to restore services to most of its customers, leaving less than 1,000 without service.

"The majority of the problem is power," said TransACT corporate communications manager, Geoff Harris. "We were able to restore over 80 percent of customers when it came back up yesterday".

Telstra and TransACT share a common problem. The service is hardest restore in areas where the weekend firestorms destroyed power poles carrying copper and fibre optic cables and fibre optic conversion nodes.

TransACT said it was still unable to ascertain how many of its nodes had been lost in the fire. Each node which converts fibre optic signals into a form that can be carried on copper, serves around 50 homes.

For now it appears that crews are looking to temporary measures to deliver basic telephone services.

"As an interim fix we'll lay cables along the ground or along fences, just to get the phones up and running," said Scott.

Once electricity supplier ACTEWAGL replaces the burnt out power poles, Telstra will go in and replace the temporary cables with more permanent ones.

Telstra has set-up temporary phone booths in Duffy and its distributing pre-paid phone cards to local residents. It is also handing out 300 CDMA phones from a mobile office it has sent to the suburb.

Both Telstra and TransACT will today send crews to compile damage reports in the most severely affected suburbs.

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