Abstract: A central processor scans a plurality of ports for the purpose of receiving data or signaling information from a peripheral acting as an information source or for transmitting information to a peripheral addressed to receive that information. The processor selectively stores that information as an image of selected conditions at each port peripheral. The transmission of information between peripherals is accomplished on a timed schedule from the centrally located processor which uses the stored image to monitor local conditions at each peripheral without the need to specifically address each peripheral. Additionally, peripherals are arranged in modules to permit simultaneous exchange of information between ports.