To increase reliability of a control system, a redundant pair of ENCS-3's can be used.
Two ENCS-3's are coupled with a CAN link, or over Ethernet in case .648EX model is used. Only one of the RTUs is active at any time. It polls devices and communicates with the upper level. The active RTU reports its status to the inactive one and switches roles if it loses connection with the polled devices.
Two ENCS-3's operate independently and poll the same devices being connected to the different ports.