Coherent Selected by Viatel as Worldwide Echo Canceller Supplier.

LEESBURG, Va.--(BUSINESS WIRE)--August 13, 1997--Coherent Communications Systems Corporation (NASDAQ: CCSC) has been selected by Viatel Inc., a facilities-based provider of national and international long-distance telecommunications services to more than 230 countries and territories, as its exclusive supplier of echo cancellation equipment for its worldwide network.

After extensive testing, Viatel selected Coherent's EC-6000 Series 2 Digital Echo Canceller to further enhance voice quality throughout its network. Coherent's EC-6000 is known throughout the communications industry for its ability to provide call clarity and cancel echo completely.

"For Viatel, Coherent's products will help ensure our ability to continue to provide superior voice quality for our customers," stated Michael J. Mahoney, President and Chief Operating Officer. "Excellent voice quality continues to be a key differentiating factor for Viatel, and with Coherent's proprietary technology, Viatel will be providing the best possible long distance quality to our users."

Designed to exceed the new ITU-T G.168 Recommendation, the EC-6000 Series 2 Echo Canceller features Coherent's state of the art RISC devices, providing a flexible and fully future-proof platform for consistent, reliable performance. The echo canceller's design also includes optimization features to ensure superior "subjective" voice quality and fail-safe facsimile transmission.

"Viatel is an example of how our products are being used by a competitive service provider," said David Powell, President and COO of Coherent. "With telecom deregulation in Europe on the horizon, we look forward to building on our relationship with Viatel, and continue to work in this competitive new marketplace."

The Coherent echo canceller uses patented Non-Linear Processor (NLP) techniques, as well as fast and stable convergence (less than 50ms for combined ERL and ERLE of 35dB) - both prerequisites for modern network applications. In addition, the unit features local loopback facilities, extensive alarm reporting and self-test diagnostics, as well as significantly reduced power consumption for improved performance and reduced heat generation. The Coherent EC-6000 Series 2 Digital Echo Canceller supports a full range of application-specific Coherent software, enhancing the unit's adaptability for a wide range of problem-solving in different network situations. Software can be remotely downloaded and upgraded, providing a versatile and cost-effective means of maintaining maximum operational flexibility as the network changes. The echo canceller not only supports configuration and control locally, via a hand-held terminal, but also remotely via a PC or other terminal.

Headquartered in New York, NY, Viatel, Inc. has network operations in seven European countries, the United States, Latin America and the Pacific Rim. The company offers a broad array of competitively priced, value-added international and domestic long-distance services, with a customer base composed primarily of small and medium-sized businesses. Viatel provides long-distance service to more than 230 countries and territories worldwide through its international network and is listed on the Nasdaq stock exchange under the symbol "YVTL".

Coherent Communications Systems Corporation is a worldwide leader in state of the art voice enhancement technology, that spans echo cancellation platforms and associated network software. The Company's products are used globally by major wireless and wireline telecommunications companies and network operators, including AT&T Wireless, BT, Cable & Wireless, Cellular One, Cisco Systems, Deutsche Telekom, France Telecom, KDD, Mercury, Nokia, NORTEL, Telia, and Telmex, among the extensive list. Coherent is a fully accredited ISO 9001 company, dedicated to maintaining the highest quality standards.

Also available via Coherent's Web Page: http://www.coherent.com

CONTACT: Diane McClelland at Coherent(tm) [phone]

Lee Feldman for Viatel [phone]

Georgina Garrett at Garrett Axford [phone]

E-mail: [e-mail]

E-mail: [e-mail]