The number of exchanges to be upgraded is not set. "It depends on the customers putting their hands up," said Denis Mullane, Telstra wholesale general manager, data business development. "If they want it and enough registrations come in, we'll do it."

The threshold level of registrations of interest required to upgrade the exchange varies, according to group managing director of Telstra broadband, Bruce Akhurst, and is based on the cost involved with the upgrade. "Each business case will get a green light when it reaches that threshold, and how fast that's going to happen is really in the hands of the individuals out there, whether they want it or not, but we won't be spending Telstras capex willy-nilly in areas where people aren't interested or it's totally uneconomic," he said.

"If your local community can get interested in the service then we'll roll it out, it's just good business for us. It's targeted investment, it's responsible investment, it's a good service to our customers," said Akhurst.

The service is based on a similar model from the United Kingdom, and will dictate which exchanges will be ADSL-enabled now that Telstra has spent AU$1 billion upgrading the main servers. Telstra announced today that the exchange in Warner, Queensland was the 1,000th to be ADSL-enabled, with 85 percent of telephone lines and 75 percent of the population now serviced by ADSL.

There are 334 ADSL-enabled exchanges in NSW and the ACT, 254 in Victoria, 205 in Queensland, 112 in Western Australia, 61 in South Australia, 27 in Tasmania and seven in the Northern Territory.

Although Telstra confirms each registrants interest in installing ADSL, the registration of interest is not a contract.

"The overseas experience has indicated that you might get some people in who allow their number to be put on the register with no intention of ever taking the service up, but it's almost negligible," said Akhurst. "If people go to the point of registering, or allowing their number to be registered, it is almost always legitimate. The reasons you may find someone who has registered no long wants to obtain an ADSL service in the future is more around the reasons that they've moved house or they're no longer there…rather than they don't want broadband."

"There's just an ever increasing interest in broadband rather than the other way around," said Akhurst.

Telstra uses Alcatel supplied Customer Multiplexer Universal Exchange (CMUX) to enable exchanges for ADSL. In terms of technical limits to the number of services in an exchange, the size of the building is one limit…the building at Warner is a demountable building," said Mullane. "As an area grows like that, we now have plans to build a brick building there as a larger exchange building, and with that sort of building there's no limit at all really. We always build in line with demand, if the customers are there we'll match the demand, we want the business."

"The technology will continue evolving as it always does," said Mullane. "We're focussing here on ADSL, but Telstra continues to look at other technologies, as it always has. The economics of technology versus the dispersion of customer base etcetera is an ever challenging situation for service providers…We need to select the appropriate mix of technology for the situation."