I'm currently between gigs as they say. When I am working, I'm a Linux/UNIX system administrator, not in electronics.
Most of the places I've worked have been company data centres which are pretty boring as it's just row upon row of locked, grey cabinets with no way of knowing what's in them. Some of these places are huge though.
Security is pretty tight and all mobile phones whether they have a camera or not, are banned. All doors are locked and need a security guard to provide access - no swipe or proximity cards are used.
When you are allowed in to work on a system, you are granted access to a particular cabinet or groups of cabinets and you're not allowed to be anywhere accept in proximity to those cabinets otherwise you're escorted from the premises. On the plus side, the guards are not armed