The waveform monitor displays the video signal as a voltage measured over time. The vertical axis is calibrated in IRE units (Institute of Radio Engineers): 0 IRE is blanking, 7.5 IRE is black (NTSC setup/pedestal), 100 IRE is peak white. Sync pulses extend below 0 down to −40 IRE. The horizontal axis represents time — one full scan line from left to right, including blanking and active video.

A real waveform monitor shows the complete signal structure: front porch (brief blanking before sync), sync tip at −40 IRE, breezeway, color burst (the 3.58 MHz sine wave on the back porch used as the chroma phase reference), then active video. The interactive display above shows this structure. SMPTE color bars have two distinct line types in the frame — top bar lines (the 7-color staircase) and bottom strip lines (−I, white, +Q, PLUGE) — use the toggle to switch between them.

Key levels: Black (pedestal/setup) sits at 7.5 IRE for NTSC. Active video must not exceed 100 IRE in broadcast — anything above is illegal white and will clip on transmission. On 75% bars, white reads ~77 IRE — this is correct. The bars are called "75% bars" because the chroma amplitude is 75% of nominal. The luma values still span most of the range.

Setting levels from color bars: Play the color bar section at the head of tape. Adjust video level (gain) until white reads the expected IRE for your bar type. Adjust setup until the black bar reads 7.5 IRE. Set gain first, then setup — adjusting setup shifts all levels, which can throw off your gain reading.

The vectorscope displays the chrominance component as a Lissajous figure. Phase angle (rotation around the circle) represents hue. Distance from center represents saturation. A signal with no color information (black, white, gray) appears as a dot at the exact center.

With properly calibrated SMPTE 75% bars, each color dot lands inside its target box on the graticule. The six colors form a rough hexagon: Yellow (10:30) opposite Blue (4:30), Red (1:00) opposite Cyan (7:30), Magenta (3:00) opposite Green (8:30). If all dots rotate together, chroma phase (hue) is off. If dots are too far from or too close to center, chroma level (saturation) needs adjustment. The dashed circle marks the expected saturation for 75% bars — your dots should sit right on it.

The Fl (flesh tone) line runs between Red and Yellow, at roughly 11 o'clock. Human skin tones of all complexions fall along this line when the signal is correctly white-balanced. If someone's face consistently plots away from this line, there is a color temperature mismatch or chroma phase error.

Blue-channel-only trick: Many monitors have a blue-only mode. With SMPTE bars in blue-only, the bars should appear as alternating equal-brightness bands. If they are unequal, chroma phase or level is off. This is a fast way to check calibration without a vectorscope.

PLUGE (Picture Line-Up Generation Equipment) is the narrow black and sub-black signal in the lower portion of SMPTE bars. It consists of three pulses: −2 IRE (below black), 0 IRE (absolute black), and +4 IRE (just above black).

To calibrate a monitor's brightness control: lower the brightness until all three PLUGE bars are invisible (crushed to black), then raise it just until the +4 IRE bar becomes barely visible as a distinct lighter tone while the −2 IRE bar remains invisible. This ensures the monitor is neither lifting blacks (milky shadows) nor crushing below black (lost shadow detail).

PLUGE calibrates the monitor, not the signal. The waveform monitor is used to calibrate the signal itself.