MES Systems CCTV Metal Warning Signs. Customers and Collection onlyBranded MES System CCTV warning signs can be a good deterrent to potential criminal activities by making individuals aware they are being observed and that the system is maintained by a SSAIB approved installer. This particular sign comes with matching screw caps covers. Also, it can be particularly valuable in public spaces, workplaces or residential areas where individuals may have concerns about their personal safety. MES offers three different