What is NEBS?
NEBS stands for "Network Equipment-Building System"
NEBS describes the environment of a typical Regional Bell Operating Company (RBOC) Central Office (CO). This description includes spatial and environmental criteria. Typical equipment line-ups are described including the environment they're exposed to.
NEBS was developed by Bell Labs back in the 1970s to standardize equipment that would eventually be installed in a CO. The intent was to make it easier for a vendor to design equipment compatible with a typical RBOC CO. This would result in lower development costs and ease the equipment's introduction into the network.