Here we have the Outboard processing gear for your studio, things like Compressors, Equalizers, Pre-amps, Multi-effects, and Analogue to Digital converters. These units can be Modular or can be Rack mounted.
A Lot of Professional Studio equipment is designed to sit in a Rack Mount unit known as a 19" Rack because of its width. The Height of the modules designed to go inside it is set as a standard known as "1U" or One Rack Unit whose height is standardised at 1.752 inches (44.50mm).
Although technology has changed a lot over the years, this format has remained the same.
500 series or 'Lunchbox' units, are smaller than average modular tools such as Compressors, channel strips etc. They can be carried around in these nice compact units....