Arcus has a roughly medieval level of technology; however, a few things that might be considered "modern" conveniences aren't unknown, including:
-Indoor plumbing
-Refrigeration
-Heating/Cooling Systems in homes.
However, these are usually produced by magical means, and often times only available to the upper class or in public places.
A few things do not exsist, or do not work, in Arcus at all, including:
-Cars
-Radio
-Television
-Light Bulbs
-Guns/Other Firearms
-Other things of an electrical nature
Some items are found in Arcus-transported in with the Crossers-and do not work, but are highly rare and valued:
-MP3 Players
-Cell Phones
-Portable Game Devices
-Books [Unreadable to most-only a handful of crossers are old enough to read, and only a few translations of crosser books to the text used in Arcus exist.]
-Other small items of that nature.
In addtion, Clothing patterned after items worn by Crossers on their arrival aren't unknown, but not particularly common or popular.