Purpose.

The Vertical Interval Reference (abbreviated VIR) signal is a program related* reference signal inserted during the vertical blanking interval of a color television program. It is intended t o reduce undesired variations in color throughout thetelevision system by assisting television producers and operators in adjusting various signal parameters BO that different programs and program segments will have similar amplitude and phase characteristics whether viewed sequentially on the same channel or on different channels.

*Program is used in a general sense and includes complete programs, commercial, spot announcements, etc.