Hayes Microcomputer Products, Inc.

George R Thomas

Randy D Nash

Taruna Tjahjadi

Matthew F Easley

German E Correa

Cynthia A Panella

John N Martin

Steven R Sweitzer

David F Strawn

Martin H Sauser, Jr

Jeffrey Inskeep

Michael L Rubinstein

Charles H McCorvey, Jr

A modem with improved signal processing and handshaking capabilities as described. Two digital signal processors are used to perform independent, concurrent operations so that a faster execution rate is obtained and more precise calculations are made possible. The modem also uses an improved handshaking technique which allows the modem to maintain compatibility with existing 1200 and 2400 bps modems while allowing for negotiation for 4800 and 9600 bps communications. The modem also incorporates an improved baud clock recovery circuit which dynamically adjusts the actual sampling point in a manner dependent upon the difference between the actual sampling point and the optimal sampling point. This allows the actual sampling point to converge upon the desired sampling point at a high rate while minimizing jitter around the optimal sampling point.

High speed half duplex modem with fast turnaround protocol

An improved V.22 bis 2400 bits per second (bps) handshake sequence detector. An incoming phase keyed (PSK) handshake sequence is autocorrelated using a frequency shift keyed (FSK) receiver (101). The autocorrelated signal is then filtered by a low pass filter (106). The autocorrelated, low pass filtered signal is then alternately fed, at a 1200 Hz rate, to two detectors (114,116). Each of the detectors (114,116) looks for one half of the handshake sequence. The output of each detector (114,116) is provided to an OR-gate (122). The 2400 bps handshake sequence is declared to be detected when either one or both of the detectors (114,116) detects its corresponding portion of the sequence.

Autocorrelating 2400 bps handshake sequence detector

A memory (90) comprising a non-volatile memory and a volatile memory, contains a test word and other words which represent a complete user-selected configuration profile. The configuration profile is stored in the memory (90) by a microprocessor (36) automatically when power is interrupted. A second power supply (80) provides operating power to the memory (90) so that the memory (90) can complete its storage cycle even after primary power has failed. The microprocessor (36) checks memory (90) for the test word to verify that the memory (90) has been programmed with a configuration profile and is not missing or defective. The modem (12) resets when power is first applied and when the power supply (75) noise exceeds a predetermined safe level. A concealed jumper strap (61) allows for the reversible placement of the modem (12) into a 'dumb' mode wherein the configuration profile cannot be altered.

Modem controller

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Marietta, GA, United States of America

George R Thomas