These are In Panel I/O blocks with short and open circuit detection. Local LEDs indicate the open or short circuits. The short circuit detection is at the sensor level and protects all the other inputs from the short. By preventing the short from effecting other inputs/outputs and the block itself from the short – the time to find the short in the field is dropped from minutes or hours to seconds. Easy I/O instance type reporting of the short or open or short back to the master allows for even faster detection of the fault on the display.