The device contains a central processing module, I/O module, and time/date facilities. The central processing module is responsible for all protocol emulation, data acquisition, and executing control requests. The device accepts commands from the master station, performs address recognition, assembles response messages in accordance with the received command, and transmits these messages to the SCADA/DMS master station. The unit also provides interfaces for a time standard and a test set. Each I/O module is capable of interfacing with digital inputs, control output points, and combinations of point types. I/O modules are also replaceable without reprogramming, redefining configuration parameters, or rewiring.