A set of standards for telecom equipment, first established by Bell Labs in the '70s and now handled by Telcordia Technologies Inc.
NEBS involves things like physical and electrical protection: Can the box survive an earthquake? What kind of electromagnetic interference does it generate? Does it catch fire? (A serious concern, given how hot some modern microprocessors run.) Designers need to take into account factors such as airflow and cooling to make sure they've got the right answers to these questions.