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Digital Microwave Voice and Data Link Gives Ebasco Access to SBS Services
Communications News, Oct, 1985 by W. Cooper
There's a new digital microwave voice and 56-kb/s data link between Ebasco Services and Satellite Business Systems (SBS) in downtown New York City. The installation demonstrates a new and promising approach to customer access to interexchange common carriers in a crowded urban environment.

Using a Harris Farinon DM18 microwave terminal and two-foot parabolic antenna mounted inside its 77th floor World Trade Center office, Ebasco transmits and receives at an angle through a narrow glass window facing the SBS rooftop antenna six-tenths of a mile away at Number One State Street Plaza.

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The digital path presently is equipped with three T1 channels and more are planned. It gives Ebasco direct high-speed data and voice access, through the nationwide SBS Network, to PBXs and computers in regional offices for exchange and processing of administrative, computer-aided design (CAD) and scheduling data. We found that putting the antenna inside the office and shooting through a window was substantially less expensive than an outdoor installation.

Ebasco Services, a subsidiary of Enserch Corporation, is a worldwide engineering, consulting and construction firm with offices in 15 US cities and 10 foreign countries.

SBS, a major interexchange common carrier, provides a family of SBS Skyline long-distance services to commercial and residential clients. The SBS Network includes four satellites, earth stations and switching centers in major cities, and extensive terrestrial facilities throughout the United States.Digital Microwave Voice and Data Link Gives Ebasco Access to SBS Services
Communications News, Oct, 1985 by W. Cooper
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Ebasco developed a mathematical model that showed emission would be substantially lower, then had an independent consultant make field tests that verified the model. Finally, we had certified health physicists from Ebasco's Envirosphere subsidiary conduct a second test. The model was again confirmed. The only measurable radiation was found in the area directly in front of the antenna, and the level was only a small fraction of the Port Authority standard. Elsewhere, no radiation could be detected at all. The Port Authority was satisfied.

With that digital path established, the leased analog circuits were replaced with digital voice and data circuits. It was turned up for service in January, 1984. In the following year, outages from all causes including rain interference totaled less than 15 minutes,a dn bit-error rate has averaged around 1X10.sup.-12.

Based on that successful experience, Ebasco began talking with SBS about a direct digital-microwave access to the SBS Network, eliminating the need for analqg leased-telephone lines. And, there was the added potential of high-speed data service to its regional offices and major clients.

The SBS response was enthusiastic. Robert McGuire, regional manager, and George Reither, communications systems manager, saw the potential, not only for Ebasco, but also for other SBS clients in New York and elsewhere. It would be a clean digital interface between Ebasco's facilities and the SBS Network. Voice circuits could enter SBS' DMS-250 digital switch directly via T1 ports with no intervening multiplexers


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