REC 501 ANSI X3.28 Half-Duplex Protocol Technical Manual

This technical manual describes the ANSI X3.28 half-duplex communication protocol used in the REC 501 device, detailing its three-layer ISO OSI model structure including physical, data link, and application layers. It provides specifications for frame formats, polling procedures, address maps for digital inputs/outputs, analogue data, events, and system parameters for master-slave multidrop communication.