What is the recommended spacing for a rack-mounted unit (RMU)?

The recommended spacing for a rack-mounted unit (RMU) is 1.75 inches (45mm). This specific measurement is standardized across the telecommunications and data center industry to accommodate the mounting of equipment in a 19-inch rack. The 1.75-inch spacing allows for consistent alignment of equipment and ensures compatible fitment of various devices such as servers, switches, and patch panels. This specificity is crucial for maintaining proper airflow, access for wiring, and overall organization within the rack system. Additionally, using this standardized spacing supports the proper installation and removal of equipment, which is essential for any maintenance or upgrades within a data center or equipment rack.

In contrast, the other options do not align with industry standards, resulting in potential complications during installation or equipment management.