In a context diagram, "Maintainer" is typically an external entity, providing both activities $($i$.$e$.,$ "maintenance"$)$ and materials $($e$.$g$.,$ spare parts$)$ to the system, and the system providing diagnostic data to the maintainer.

Give two examples of real$-$world systems where this would be the case $($maintainer action and system diagnostic data back to the maintainer$).$