Busy Box and related
The Busy Box is located in the DAQ Counting Room. Its purpose is to halt the data taking when the system is saturated with event data. When the multievent buffers in the Front End Electronics run full, the Busy Box asserts a busy-signal to the Local Trigger Unit which halts the issuing of new triggers. The the busy-signal will be deasserted once there are available buffers.
To calculate the number of used mulitevent buffers the Busy Box listens to the trigger system to see which events have been triggered, and then poll all the DRORCs to see which events have been transfered to DAQ.