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DSP-based Modem Software Targets Digital Telephony

Programmable design uses general purpose DSP and downloadable code to provide modem compatible with digital communications channels.

San Francisco, CA, June 13, 1994..... VOCAL Technologies, Ltd., a leading supplier of DSP-based communication technologies, today announced a new version of their modem software which provides full support for 8 kHz sampling rates, the standard data rate used in most digital telephony systems. VOCAL's modem software runs on the Analog Devices ADSP-21xx family of processors and is specifically designed to support OEM peripherals without requiring special ASICs. Developed by VOCAL's Custom Product Design Division in Buffalo, NY, the software is intended for cost and performance sensitive OEM applications where the economics of the production run cannot justify migration to full custom silicon. VOCAL designs provide customers with faster time to market, proven hardware/software implementations, and flexibility. Typical applications include modems for embedded designs such as security systems, PBXs, dial up routers, channel bank modems, and telephony on T1 and E1 lines.

The VOCAL approach to modem design is based on the principle of using a single general purpose DSP to perform all the modem modulations. The Company's original product provides traditional modem functionality, all the ITU (CCITT) specified modulations includingmultiple data and fax protocols, command sets, and other telephony functions such as DTMF generation and call progress detection.

Perceiving an unmet need in the digital telephony marketplace, VOCAL adapted its modulation software suite to operate at an 8 kHz sampling rate. Direct acceptance of 8 kHz data allows digital telephony products based on the VOCAL modulations to interface modem capabilities seamlessly to digital telephony trunks and lines. According to Frederic Hirzel, VOCAL's president, "Our approach maximizes the advantage of today's DSP chips and gives our OEMs the lowest possible design costs. By keeping the functionality in software, we do not require our customers to use special chips or ASICs, and we hold the promise of future upgradability and compatibility with emerging standards."

Though modems are conventionally connected to analog telephone lines, the need for a digital telephony modem is surprisingly common. Manufacturers of digital PBXs and T1/E1 channel banks can both benefit from a modem which operates at an 8 kHz sampling rate. Conventional modems typically operate at a 7.2 kHz sampling rate, thereby making them difficult to integrate within digital telephony products.

Previous digital telephony products with integral modems have had difficulty using conventional modem solutions. External hardware must be added between the modem and the digital sample stream. For example, if the traditional modem has a fixed digital sampling interface, typically operating at 7.2 kHz, an additional DSP is used to rate convert the sample stream from 8 kHz to 7.2 kHz. If the traditional modem has only an analog interface, an additional voice codec is used to convert the 8kHz sample stream to analog; the modem then operates on the analog signal. The VOCAL 8 kHz modem completely eliminates the need for this extraneous interface hardware. By operating at a native 8 kHz sampling rate, the VOCAL design allows direct connection to digital telephony data, saving OEMs hardware complexity and costs.

VOCAL software can be customized by an OEM for a particular hardware configuration, and/or used with VOCAL's low cost, royalty?free, reference design. VOCAL's engineers have taken advantage of the superior price/performance of Analog Devices' fixed point ADSP-21xx family to provide an easily customizable modem system which requires no special hardware and which can be upgraded in the field by simply downloading new software.

VOCAL's DSP modem software is available as individual modules, as a complete suite, or as part of a turn-key hardware/software solution. The software is available immediately. Pricing depends on the exact OEM configuration and modulation set required, and can range from fixed fees of $25,000 - $350,000, or can be licensed on a per unit royalty basis. VOCAL provides comprehensive integration and support services.

VOCAL Technologies Ltd. provides full service telecommunication and networking solutions to OEM customers and systems integrators in the USA and abroad. VOCAL's expertise includes the development of hardware and software for modem and router applications ranging from remote access, portable computing, networked-based data communications, telemetry, as well as Central Office equipment.VOCAL's engineering team can assist OEM customers throughout all phases of a project, from specifications to design, testing, prototyping, manufacturing, and end-user warranty support.