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Read-Out System - A sub-system of the ATLAS TDAQ responsible for reading out the ATLAS RODs and for supplying event fragments to the LVL2 and EB sub-systems.
ROD
Read-Out Driver - The detector specific Front-End Functional element which gathers data from the derandomizers over one or more data streams and builds ROD fragments of events to be sent to the ROS or RoIB.
RoIB
Region of Interest Builder - The element which combines RoI information from different parts of LVL1 and forwards it to a LVL2 supervisor.
RoI
Region of Interest - A region limited in eta and phi, indicated by the LVL1 trigger to contain candidates for objects requiring further computation.
ROB
Read-Out Buffer - Standard module which receives data from on or more RODs, stores them and makes them available to the LVL2 trigger processors and, for LVL2-selected events, to the EB. Data are stored during the LVL2 build time and for selected events until the Event event is built inthe in the EB.
ROBIN
Read-Out Buffer Input Stage
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Read-Out Driver - The detector specific Front-End Functional element which gathers data from the derandomizers over one or more data streams and builds ROD fragments of events to be sent to the ROS or RoIB.
ROL
Read-Out Link - The physical link between ROD and ROS through which the data are sent at the event rate of the LVL1 trigger.
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Read-Out Crate - The combined functionality of the LDAQ, TRG, EBIF and one or more ROBs.
RoI
Region of Interest - A region limited in eta and phi, indicated by the LVL1 trigger to contain candidates for objects requiring further computation. In the case of B-physics triggers at low luminosity, some ROI's may be defined internally within the level-2 trigger system.
RoIB
Region of Interest Builder - The element which combines RoI information from different parts of LVL1 and forwards it to a LVL2 supervisor.
L2PU
Level 2 Processing Unit - The L2PU is the application running on one of the Level-2 processors, hosting the HLT processing algorithms and also incorporating the calculations from which the LVL2 trigger decision is derived.
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