NEBS (Network Equipment-Building System) describes the environment of a typical United States RBOC Central Office.
NEBS is the most common set of safety, spatial and environmental design guidelines applied to telecommunications equipment in the United States.
The objective was to make it easier for a vendor to design equipment compatible with a typical Regional Bell Operating Company (RBOC) central office (CO).
NEBS Level 3 has strict specifications for fire suppression, thermal margin testing, vibration resistance (earthquakes), airflow patterns, acoustic limits, failover and partial operational requirements (such as chassis fan failures), failure severity levels, RF emissions and tolerances, and testing/certification requirements.
For physical protection, good engineering practices cover metal surface treatment and contact compatibility, flammability ratings, component marking and traceability, electrical and mechanical integrity, and a variety of process manufacturing issues.