The DY-5545M Single-Channel Dual-Loop Self-Healing. Fully Redundant Ring – industrial, serial to optical transceiver. It is a low-cost serial data transmission communication device with dual-ring self-healing function that can adapt to industrial environments. It can form a chain network or a dual-loop fiber network for the transparent transmission of one RS-232/RS-485/RS-422 signal on the fiber ring network. Provides superior opto-isolation.