PLUGE

PLUGE is a term used in analog television testing to describe a test pattern component that helps calibrate the black level and near-black detail of a video display. The acronym is commonly said to stand for Picture Line-Up Generation Equipment (though some sources expand it as Picture Line-Up Pattern), and the exact phrasing can vary by standard.

A typical PLUGE pattern appears as a small block or strip within a larger test pattern, often accompanying SMPTE or CCIR/EBU color bars. It includes luminance steps near the black level, including one or more bars below the display’s nominal black level and adjacent near-black levels. The purpose is perceptual: when the system is properly calibrated, the sub-black portion is just visible or disappears into the black field, while the near-black steps maintain discernible detail.

PLUGE originated with analog television systems (such as NTSC, PAL, and SECAM) and was a common tool for setting correct black level, gamma, and contrast on CRT displays. With the shift to digital video and improved automatic calibration, PLUGE has become less central, though many legacy test patterns still retain it for compatibility and historical reference. In modern practice, PLUGE may be omitted or represented as a digital surrogate in some test patterns, but its role in providing a black-level reference remains acknowledged in many video engineering handbooks.