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The logjam at the high end of DSL services seems about to break--at least in Europe--with the arrival of Symmetrical High-Density Digital Subscriber Line technology, which promises whopping transmission speeds of up to 4.6 megabits per second for both uploads and downloads.

And unlike the current high-speed, two-way DSL technology, SDSL, SHDSL is interoperable with the existing network infrastructure. Efficient Networks and other DSL equipment makers see SHDSL as the perfect business complement to Asynchronous DSL in the home market, which offers fast downstream but slow upstream. For businesses, SHDSL provides the bidirectional high-speed transfers that video, voice, and other high-bandwidth applications require.

High Speed at Wide Range

SHDSL is also able to reach 20,000 feet from central-office switches, and repeaters can extend that to a theoretical limit of 19 miles, says Shaheen Kazi, director of product marketing at Efficient Networks. Because the repeaters amplify the signal, there is no degradation, and in fact the signal is improved, Kazi adds.

Efficient's $599 5950 SHDSL Business Gateway, which will be available when the first SHDSL services roll out in Europe this summer, is targeted at small and midsize businesses, as well as at enterprise branch offices and remote workers. It features a wire-speed virtual private network and firewall for business-class security, as well as the Virtual Router Redundancy Protocol and dial backup to guarantee high availability. The device's intelligent 10/100 ethernet 8-port switch automatically detects full- or half-duplex operation and regular or crossover cable.

Besides working with existing networks, the new SHDSL standard also conforms to International Telecommunications Union G.991.2 Recommendations and uses the same data encoding and signal modulation techniques as the ANSI-backed HDSL-2 standard.

SHDSL is expected to catch on faster in Europe than in the United States because of Europe's slow adoption of SDSL. Nevertheless, Efficient Networks expects SHDSL services to become available on this side of the Atlantic by the second quarter of 2002.

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