What key sequence is depressed and held to access the BMON (controlled start) screen while powering on the controller?

To access the BMON (controlled start) screen when powering on the FANUC controller, the correct key sequence involves holding down F1 and F5 as the system boots up. This specific combination is crucial because it initiates a special startup mode that allows technicians and operators to access diagnostic and maintenance functions that are not available during normal operation.

The BMON screen provides essential tools for monitoring and controlling the system's parameters, which is particularly useful for troubleshooting or making specific adjustments during the initial setup phase. Recognizing this key sequence is vital for anyone working with FANUC systems, as it ensures proper access to diagnostic tools that can support effective system management.

The other combinations do not trigger the BMON screen, which is why they are not suitable for this specific function. Understanding the importance of the correct key sequence emphasizes the need for familiarity with operational procedures in machine control environments.