An apparatus having a two wire system for providing both power and data communication between a master controller 22 and at least one subcontroller 29, 30, 31. The master controller 22 can also be connected through the conductors 25, 26 to submaster controllers which in turn have subcontrollers connected thereto. The master controller 22 is capable of addressing each of the submaster controllers and subcontrollers 29, 30, 31 individually. A three voltage level system can be utilized to provide both power and addressing through the two conductors 25, 26. Data transmitted by the subcontrollers 29, 30, 31 can be analog and/or digital. A data entry device and an information display device can be connected to the master controller 22 in the same manner as other subcontrollers.