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