Category 1, low electromagnetic radiation environment. Typical low levels emitted by local broadcasting stations/radio stations/television stations and low-power transmitters/receivers located more than 1km away.
Category 2, medium electromagnetic radiation environment. The use of low power portable transmitter-receivers/typical ratings less than 1W but limited to use near the equipment is a typical commercial environment.
Category 3, Severe Electromagnetic Emission Environment. Portable transmitter-receiver/typical rating 2W or greater, can be used close to the equipment but the distance is less than 1m. equipment near high-power broadcast transmitters and industrial, scientific and medical equipment is a typical industrial environment.
Category 4, is an open class defined by consultation or product specifications and product standards.