In a large industrial building there are many meters measuring various quantities as well as many control devices. We divide them to for categories:
  The measurements are not particularly accurate, and the requirements on response times are not particularly strict.

We intend to control the equipment through normal serial interfaces connected to the central controller (a PC equipped with UPS and an operating system MUCH superior to Windows). The communications interface devices connected to the meters/controllers should be as simple as possible. What kind of a network and what kind of a communications protocol would you use?

Solution