mi 3,924,060  Dec. 2, 1975
 CONTINUOUS INFORMATION ADD-ON SYSTEM
 Inventor: Alan D. Bedford, St. Paul, Minn.
 Assignee: Hazeltine Research, Inc., Chicago, 111.
 Filed: June 24, 1974
 Appl. No.: 482,381
 U.S. CI 178/5.6; 178/DIG. 23
 Int. CI.2 H04N7/00
 Field of Search 178/5.6, 5.8, DIG. 23
 . References Cited
UNITED STATES PATENTS
3,806,637 4/1974 Sideris 178/DIG. 23
3,838,444 9/1974 Loughlin 178/DIG. 23
3,849,594 11/1974 Justice 178/DIG. 23
Primary Examiner—Richard Murray
Disclosed is a system for transmitting and receiving add-on information in conjunction with the transmission and reception of TV signals. In accordance with the invention there are provided first and second addon signal components in phase quadrature. The second add-on signal component has, during each TV line interval, a polarity opposite to the polarity of the first add-on signal component of the preceding TV line interval to achieve substantial visual cancellation of the add-on signal components in the displayed image. Further, the second add-on signal component is representative, during each time successive line interval, of the identical add-on information represented by the first add-on signal component during the preceding line interval. Processing means are provided for cancelling redundant video information contained in time successive line intervals and reinforcing the intentionally redundant add-on information represented by the first and second add-on signal components.
17 Claims, 5 Drawing Figures