Gefen's HDMI/DVI test device is designed to identify connection and calibration problems with complex installations, so you don't have to tear them apart to identify a fault.
It's a lightweight, portable (though mains adaptor-powered) unit with a small LCD panel and eight control buttons. On the back are an HDMI out; optical digital audio and stereo audio line inputs; RS-232 connector (for a PC control programme which can be downloaded from the Gefen website); and an Underscan/ Overscan button, together with the power connector and switch. A single HDMI cable is provided.
The HDMI signal generator runs through some basic SD and HD test patterns automatically, or you can manually select the appropriate format, resolution, and patterns.
Patterns include pure colours, gradual patterns, colour bars, greyscales, vertical bars, horizontal bars, multi-bursts, pluge (don't ask, it's too geeky), gradients, grids, circles, crosshatches and more. The manual explains what patterns are useful for what connection and calibration problems, and explains how to set up the RS-232 control software.
The unit supports RGB and YUV colour spaces, PC and HDTV signal timings, PAL and NTSC frame rates, and can generate an HDCPencrypted signal to test compliancy. It will also output audio tones in 2, 4, 6 and 8-channel over HDMI (or will accept your external stereo inputs).
Too advanced and expensive for the needs of the average domestic user, but then, bear in mind that it is aimed at professional installers, and wouldn't they appreciate a ruggedised, battery-powered, ergonomic version?