Specifications

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Although Ethernet is usually thought of as having a star topology, it’s also possible to build an Ethernet
network as a ring. This configuration has the advantage of providing a redundant pathway if a link goes
down. A ring topology is often used in applications such as traffic signals and surveillance, where long
distances may make it difficult to run fiber in a star formation from a central switch and where downtime
must be minimized.
The key to the ring topology is spanning tree protocol. One switch—in this case, the switch in the central
office—is the root of the spanning tree. A node on the opposite side of the ring blocks one of the ports
leading back to the root switch, creating a topology that functions like a long line of Ethernet switches.
If a link breaks, the network reorganizes itself to relink all the switches. Although this convergence isn’t
instantaneous, it takes only a few seconds to bring the network back.
In the diagram below, Hardened Managed Ethernet Switches create a ring topology that operates at Gigabit
speed to support traffic cameras at the intersection. Industrial Ethernet Serial Servers make the connection
from the switch to the serial interface on the traffic signals, enabling central management
of the lights across the Ethernet network.
Fiber ring topology provides
both distance and resilience.
RS-232 Cable
(EDN12H)
Single-Mode Fiber Optic Cable
(EFN310-005M-SCSC)
Hardened Managed Ethernet
Switch (LEH808-2GLXSC10),
facing page
Industrial Ethernet Serial
Server (LES404A)
Industrial Ethernet Serial
Server (LES404A)
Traffic Light
Traffic Camera
Traffic Light
Traffic Camera
CAT5e Cable
(EVNSL81)
Root switch in Central Office
Traffic Light
Traffic Camera
Traffic LightTraffic Camera
Industrial Ethernet Serial
Server (LES404A)
Hardened Managed Ethernet
Switch (LEH808-2GLXSC10),
facing page
RS-232 Cable
(EDN12H)
RS-232 Cable
(EDN12H)
RS-232 Cable
(EDN12H)
CAT5e Cable
(EVNSL81)
CAT5e Cable
(EVNSL81)
CAT5e Cable
(EVNSL81)
Industrial Ethernet Serial
Server (LES404A), page 4
Hardened Managed Ethernet
Switch (LEH808-2GLXSC10)
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Tech Support: 030-241 77 99 | Sales: 030-241 77 77