a term used to describe the mounting of certain types of audio visual equipment - especially in outside broadcast vehicles and recording studios.
Rack mounted equipment always conforms to a standard width of 19 inches (approximately 40 cms) hence the term 19| rack mount. The height of a standard piece of 19" rack equipment is known as 1U or one unit. This can be as high as 2m3 or 4 units depending on the equipments role. ("Half U" means rack equipment that is able to it in pairs along side each other in 1 rack unit or "U"
Rack mixers are mixers designed to mount into 19" rack mounting cabinets.