This document, in conjunction with ANSI/EIA-709.1-A Control Network Protocol Specification, defines a complete 7-layer protocol stack for communications on an EIA-709.4 single-fiber (half-duplex) fiber-optic channel. This channel supports communication at 1250 kbps between multiple nodes, each of which consists of a fiber-optic transceiver, a protocol processor, an application processor, a power supply, and application electronics. The single-fiber channel implemented as specified herein allows two nodes to communicate bidirectionally across a single piece of fiber cable -- thus minimizing complexity of the fiber interconnect.