A flexible protocol communications approach for a supervisory system

This paper deals with the communication protocol intended to control up to 1016 devices of a new supervisory system. It has been conceived in two complementary phases. The first one (Cycle-A) is intended to inform the Central Station of any event detected by the installed devices in less than two seconds. The second one allows to set up a link between the Central Station and a selected Local Station in order to request more information or to action its devices for command or programming purposes. The dialog between the Central Station and the Local Station takes place on a two wire communication channel, also used to supply de current from the Central to all Local Stations.