Vectorscope

The vectorscope's graticule roughly represents saturation as distance from the center of the circle, and hue as the angle, in standard position, around it.

The reference signal used for the vectorscope's display is the colorburst that is transmitted before each line of video, which for NTSC is defined to have a phase of 180°, corresponding to the -U position on the graticule.

The actual colorburst signal shows up on the vectorscope as a straight line pointing to the left from the center of the graticule.

In the case of PAL, the colorburst phase alternates between 135° and 225°, resulting in two vectors pointing in the half-past-ten and half-past-seven positions on the graticule, respectively.

On older vectorscopes that use cathode-ray tubes (CRTs), the graticule was often a silk-screened overlay superimposed over the front surface of the screen.

One notable exception was the Tektronix WFM601 series of instruments, which are combined waveform monitors and vectorscopes used to measure CCIR 601 television signals.

The combined device is typically referred to as a waveform monitor, and standalone vectorscopes are rapidly becoming obsolete.