CYGNUS 891 Fiber Ring for RS232

CYGNUS 891 is a Ring formed by interconnecting fiber segments and CYGNUS 891 Nodes. It allows point-to-point connections between a central site and multiple locations extended on the fiber ring. If a fiber segment between two nodes on the ring get cuts or if a node itself malfunctions communication continues in the other direction


  • CYGNUS 891 allows a number of Async user devices to communicate with each other over an optical fiber ring.
  • Available in two models. 891R offers 1 or 2 user ports. 891C offers 4 or 8 user ports
  • Supports point to point and multipoint networking between user devices
  • Each unit has 2-way fiber connectivity to other nodes and acts as a node in interconnected ring or linear topology.
  • A CYGNUS 891 based fiber ring can have up to 32 nodes in case of multipoint half-duplex communication, and 9 nodes in case of point to point full-duplex communication between user devices
  • Offers ring protection, i.e., handles failure of one segment of the ring through redundancy in data transmission.
  • Point-to-point full-duplex connectivity between any two user ports on 891 units in the ring, OR
  • Multipoint half-duplex connectivity network between a number of user ports which share the same virtual circuit. Each such multidrop network can have its own master and slave devices distributed over the fiber ring.
  • For use in point to point applications 891R may be ordered with RS232, RS422 or 20 mA current Loop user interfaces, while 891C may be ordered with RS232 or RS422 interface. For multipoint half duplex applications both 891R and 891C may be ordered with 2-wire RS485 interface.
  • Option of 1500 VAC isolation protection is available for RS232, RS422, RS485 and current loop interfaces.

Application Diagram