Since copper telephone networks were not made with high-speed data services in mind, one of the technical problems marring the DSL rollout has been the location and assessment of bridged taps and load coils.

"The copper telephone network was not deployed with the intent to support high-speed data services," said Frank Bauer, director of advanced technology at Teradyne's Broadband Test Division. "In today's copper loops, speed impairments such as imbalances, bridged taps and load coils exist on a significant percentage of the lines."

Unmasks bridged taps

Teradyne estimates, through research done in conjunction with U.S. local exchange carriers (LECs), that bridged taps could exist on as many as 75 percent of copper lines.

Generally, when deploying ADSL, LECs will remove bridged taps as part of conditioning the network for broadband service. But that process of finding and removing bridged taps and load coils using plant records and field dispatches is less than efficient. The Celerity Ti (bridged "Tap impact") detects the presence of bridged taps and their operational impact by performing single-ended measurements through the narrowband switch test bus installed in voice switches.

Market-research firm Frost and Sullivan believes that the market for testing DSL equipment is poised to grow, generating revenue of $169.2 million in 1999, and nearly $600 million in 2000. This growth is attributed to the markets' developing nature. Growth is expected for the next several years, with revenues projected to top the $2.5 billion mark by 2006.

The Celerity Ti looks to determine if the line will support DSL service with the bridged tap left in place or removed.

Teradyne estimates approximately 55 percent of lines with bridged taps will carry DSL service at 384 kbits/second; 15 percent of lines with bridged taps will carry service if the tap is removed; and around 30 percent of lines are unusable, irrespective of bridged taps. The Celerity Ti determines which class the line falls under, thereby streamlining the LEC's line-conditioning work and ultimately speeding deployment.

"This information has significant value to LECs because they target their repair effort where it will provide most advantage in bringing broadband services sooner," Bauer said.

The Celerity Ti is available now, with pricing configured based on the network system.