A system for use in supervising and controlling temperature and other environmental conditioning equipment of a building or the like is disclosed. The system monitors and controls various types of sensors and control equipment located at remote field points. The system includes a control console and a number of field located multiplexing modules which are connected to various remote field points. Each of the multiplexing modules is connected to associated field points that are connected to each other and to the multiplexing module in a single leg circuit. The multiplexing modules and control console are also connected together. The multiplexing modules simultaneously and independently poll their associated field points and only communicate with the control console for an alarm special or changed condition. The field points include common field point modules which interface with any of various field point units which comprise sensors or control field point apparatus. The field point modules provide identification signals as well as values measured by the field point units to the multiplexing modules upon command.