Historical
NEMA TC 6 & 8:2003
Polyvinyl chloride (pvc) plastic utilities duct for underground installations
Defines general requirements, performance requirements, test methods and marking for the following types of PVC plastic utilities duct intended for underground installation for communications and electrical wire and cable: Type EB-20 and Type EB-35, designed for burial encased in concrete; Type DB-60; Type DB-100, and Type DB-120, designed for direct burial without encasement in concrete.
NEMA: National Electrical Manufacturers Association [nema]