A system and method for controlling a communications system that dynamically provides context sensitive functionality. In one embodiment, the system comprises a Private Branch Exchange (PBX) connected by communications channels to one or more communications devices and controlled, in part, by software objects that provide functionality that varies dependent on the hardware and software currently available and the status of that hardware and software. In one embodiment, the user of the communications device is presented, by way of an addressable display and associated function buttons, with only the function options appropriate to the context in which they are currently using the system. For instance, a conference option only becomes available when more than one incoming call is made to the same telephone.