Rackmount

Many items of professional audio, control and IT equipment are designed to be installed in a standard 19" rack.

Many varieties are available, ranging from small Flightcase-style units up to freestanding units over 2m tall, either open-frame or enclosed, in various depths.

The rear of the rack will generally contain various power supply systems and cable management facilities.

The common feature that all share are the front "rails". These usually have regular square holes in which a Cage Nut (or captive nut) can be inserted, and then a piece of equipment can be bolted into the rack. The equipment will have "ears" on the front to enable it to be bolted in place. Alternatively some racks come with a C shaped channel, which the nut is free to slide up and down in, but not rotate, rather than the more usual cage nut system.

1U height: 44.45mm (1 3/4 inches)

Equipment front panel width: 483mm (19 inches)

Rack opening width: 450mm

Between fixing centres: 465mm

Between rack outer edge faces: 486mm

Equipment front panel width: 483mm (19 inches)

Equipment body width: 449mm (max)

Some equipment may be "rail-mounted", where it is attached to the rack via sliders, and can be pulled forward and out of the rack, while still completely supported, for maintenance. Cable management is critical here - a hinged arm at the rear allows the cables to be controlled, yet leaves enough movement to allow the unit to be pulled forward.

When rail-mounted units are pulled out, care must be taken to ensure that the rack does not topple. Many will be fitted with extending feet or outriggers to use in this situation.

The height of devices which are mounted in such racks - and the size of the rack itself - is measured in "U" - short for "Units" - where 1U is equal to 1.75 inches. Small items such as FX units etc may be 1U high, power amplifiers may typically be 2U or 3U.

Large racks which are used in studios and equipment rooms are typically 42U or even 48U high - the upper limit often being dictated by the size of the lifts in the building!

It is possible to mount non-standard equipment by using a rack tray or shelf.

Some items are described as "half-rack" - meaning they are half width, and two can be mounted side-by-side using proprietary fixing kits.