depends on the actual building and its use aswell, im only little fish in big pond and any ive tested 2 restaurants, the key switch didnt work so i knocked off mcbs. but because the chinnese start early i was there at 9am as soon as doors open as this was appropiate time for full duration test.. so no you dont need it but if you bigger building maybe you do and if you in biger important building you might need the computer controlled version...