individual actuator position and status actuator tuning and configuration and system status interlocks are communicated between the host 20 and the gateway 22 in fig3 the host interface card 56 is an ethernet interface card this could also be a serial interface in some cases a number of protocols have been implemented with various products of measurex corporation cupertino calif usa the lan interface is based on ethernet the protocol is a measurex developed protocol open data exchange odx which is layered on top of tcp ip this type of interface is standard with current measurex product lines the common serial protocols are modbus rtu an industry standard scl measurex protocol and 200 100 measurex protocol the gateway 22 supports these protocols all of which are commercially available to insure compatibility with older products this interface consists of software within the pc 48 a network interface communications card and network router s 54 a network router 54 performs three functions a media conversion devices in the gateway such as the pc and a network management and installation tool require a 1 25 mbps channel whereas the actuators communicate at 78 kbps over a free topology channel the router provides the media conversion b extend the limits of a single channel each actuator lan channel supports up to a maximum of 62 actuators for systems with more than 62 actuators additional routers are required c improve network performance a router 54 can isolate network traffic to a channel an intelligent router can decide if a message must leave the channel based on the location of.