Universal Robots UR30 PolyScope X User Manual page 150

Under normal conditions, i.e. when no Robot stop is in effect, the safety system operates in a Safety Mode
associated with a set of safety limits
Safety mode
Normal mode
Reduced mode
Recovery mode
25.4.2. Safety I/O Signals
1
Robot stop was previously known as "Protective stop" for Universal Robots.
UR30 PolyScope X
1
:
Effect
is the safety mode that is active by default.
activates when the Tool Center Point (TCP) is positioned beyond a Trigger
Reduced mode plane, or when triggered using a configurable input.
activates when a safety limit from the active limit set is violated, the robot arm
performs a Stop Category 0. If an active safety limit, such as a joint position
limit or a safety boundary, is violated already when the robot arm is powered
on, it starts up in Recovery mode. This makes it possible to move the robot arm
back within the safety limits. In Recovery mode, the movement of the robot
arm is restricted by a fixed limit that you cannot customize.
User Manual