Trend graph display system

A trend graph display system including a cathode ray tube having a viewing screen on which time points represented by a plurality of points serially related in time spaced from one another with a predetermined time interval are displayed in the raster direction, while display quantities of trend graphs are displayed as functions of said time points in the direction perpendicular to said raster direction by respective pluralities of point s spaced from one another with a predetermined interval, each point of said respective plurality located in a different raster scan from the remaining points of said respective plurality, said cathode ray tube being so adapted that a raster scanning is effected by sweeping said viewing screen with a scanning point whereby the scanning lines thus produced are correlated to said spaced points representing said display quantities, further including;

• memory means for storing said display quantities of said trend graph corresponding to said serially related time points;
• reading means for sequentially reading out said display quantities from said memory means in the order of said serially related time points;
• and
• comparison means for comparing the display quantity read out from said memory means with a display quantity represented by an instant scan line, said comparison means comparing the display quantity read out from said memory means corresponding to an instant time point corresponding to an instant position of the scanning spot of said instant scan line on said viewing screen with a display quantity represented by an instant scan line, thereby to supply a video signal to said cathode ray tube upon coincidence being found in said comparison, said comparison means further including means for supplying said video signal to said cathode ray tube when said instant display quantity represented by said instant scan line lies in a range delimited by the display quantity at said instant time point and the display quantity at the selected one time point of the time points immediately preceding and following said instant time point.