A relay rack is a storage system used to hold a variety of networking and communications equipment. These racks date back to the 19th century, when they were used to hold railroad signaling, or relay, equipment. Today, the relay rack retains the same basic features, but the equipment it holds is dramatically different. Then and now, the standard relay rack measures 19 inches (48 cm) wide, which allows it to accommodate the average electronics equipment module. This type of equipment storage unit is also known as a server or networking rack.
While the width of the relay rack is generally fixed, its height and depth can wary by industry. Some of these racking systems are just a few feet high, while others extend all the way up to the ceiling of a room. Typically, the height of each system is given in both standard measurement units as well as a specialty measurement called a “U.” One U measures 1.75 inches (44mm). Each relay rack is also rated for a specific weight capacity based on its design and configuration.
Manufacturers produce relay racks from metals such as steel and aluminum. Each system is typically fire-rated due to the high volume of electronics equipment they are designed to hold. The vertical framing members are lined with holes, which allow users to quickly and easily mount equipment to the rack. The space between each holes measures 1U on a typical relay rack. Depending on the system, the rack may require screws, bolts, or special mounting brackets to hold each equipment module.
One of the advantages to the relay rack is that it holds multiple equipment modules within the same mounting system. This allows users to combine all telecommunications or server equipment into organized rows. The open structure of these racks also allows for access from multiple sides, making maintenance and modifications fairly easy. The rack system is also highly customizable, with configurations available to suit the needs of almost any system.
Typically, relay racks can be found in almost any corporate office building. These racks are placed in server or electric rooms to house computer equipment, network servers, and even phone systems. Relay racks are also used in more specialized facilities, such as computer centers and electronics corporations. Telecommunications facilities may use standard relay racks, though some use a larger racking system which measures 23 inches (58 cm) wide rather than 19 inches (48 cm). This allows the rack to accommodate the larger modules typically found in the telecommunications field.