The Kramer 841 Portable Computer Graphics Video Test Pattern Generator is a device for generating RGBHV signal patterns for VGA-enabled displays such as computer monitors, projectors, and some high-definition TV sets. Part of the Kramer TOOLS line, the compact device requires only a third of a single rack space in a standard 19" rack, so three similar-sized devices can be installed side by side using the optional RK-3T rack adapter (not included). It includes an internal rechargeable battery that makes it suitable for field use.