NTL plans to lease capacity on the network to other telecommunications operators rather than provide a service to consumers.
Its first customer is Vodafone, the cellular radio company, which will use the NTL system to link its mobile telephone exchanges rather than rely on BT or Mercury.
A spokeman for NTL said the network would be the first such commercially available national network apart from BT or Mercury.
'Until now there has been no other means of buying capacity on a national basis,' he said.
No value has been given for the deal with Vodafone, but it is thought to be worth a minimum of pounds 10m over five years.
National Transcommunications, which hopes to float on the stock market later this year, is talking with a variety of other potential customers for its digital voice and data links.
These are thought to include cable television companies that also operate local telephone networks and wish to link with other cable companies to provide regional telephony.
The NTL network relies on microwave links between sites already occupied by television transmitters. The company has about 600 such sites nationwide.
Energis, part of the National Grid Company, also hopes to launch a national trunk network for telecommunications using cable wrapped around the country's electricity transmission system.
But Energis' orginal launch date of April has slipped and is now unlikely to be before the autumn. NTL, whose main business is TV and radio transmission, was bought from the Government in 1991 by Mercury Asset Management for pounds 70m.
It is expected to report a turnover of about pounds 100m for 1993, compared with pounds 85m in 1992 when it made a pre-tax profit of pounds 10.5m.
Recently the company paid pounds 6.6m to acquire DTELs, a former government agency providing mobile communications for emergency services.
Cellnet, the mobile telephone company owned by BT and Securicor, is expected this week to announce plans to launch a digital mobile service that allows customers to use their telephones in Europe and provides higher quality than traditional analog networks. Cellnet has been criticised for lagging behind Vodafone, its arch rival, in offering the service, which is known as GSM.
But the company expects the digital service to be available to 90 per cent of the UK by Christmas and says it will be able to match Vodafone's coverage by early 1995. Charges for the digital service are unlikely to be higher than for Cellnet's normal analog cellular telephony.Reuse content