The GEM standard outlines a control state model to define the level of co-operation between the host and equipment. GEM Equipment provide three basic levels of host control which determine the host's ability to control and monitor the equipment. The equipment may support custom commands. Equipment constant features allow the host to set and retrieve equipment constant values which govern the equipment's behaviour. An alarm is related to any abnormal situation on the equipment that may endanger people, equipment, or material being processed.
GEM allows the host to be notified when alarm conditions are detected and cleared.
A collection event is a detectable occurrence significant to the equipment that is considered to be significant to the host. GEM allows the host to be notified when a collection event occurs. This allows the host to track the equipment's activity. Data Variable Data variables may only be valid upon the occurrence of a particular event. The host may gather data variable values from the GEM Equipment.