04672605 is referenced by 371 patents and cites 22 patents.

A high speed and relatively error free communications system is disclosed which enables the high speed transmission of data at a 19.2 kilobit per second rate. The data is transmitted over the same communications medium as voice transmissions, the data transmission being virtually imperceptible to the user of the analog telephone system. Connection to and from the data terminals is made through an RS232C interface. A spread spectrum technique is utilized which "whitens" the signals of the data terminal regardless of whether the terminal is idle, transmitting or receiving data. Virtual error free transmission is achieved by interleaving bits, so that noise does not destroy the data, and by error detection and correction techniques which assure that the data, as received, is identical to that transmitted. By using a variable pseudo random code, privacy of data communications are enhanced and cross-talk is substantially eliminated. The resulting system is one that can use a single twisted pair wire for transmission and is capable of transmitting data at a high rate of speed while leaving the analog voice transmission resident and unaffected on the line.

Title
Data and voice communications system
Application Number
6/591509
Publication Number
4672605
Application Date
March 20, 1984
Publication Date
June 9, 1987
Inventor
Robert S Bradford
Woodland Hills
CA, US
Donald W Moses
Minneapolis
MN, US
Jeffrey L Ward
Hudson
WI, US
Charles H Hustig
Hudson
WI, US
Agent
Dorsey & Whitney
Assignee
Applied Spectrum Technologies
MN, US
IPC
H04J 1/14
H04J 1/12
View Original Source