Chapter 1 - Overview; Description - TC Communications TC2400 User Manual

Rack mount/stand alone hi-speed multi-drop (ring) fiber optic modem

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The TC2400R/S and TC2401R/S are high speed multi-drop fiber optic modems designed for a ring topology

with a self-healing capability as shown in Figure 1. When connected to a SCADA host controller, the Master

unit (TC2400) can broadcast its poll messages to all the remote (TC2401) units (also referred to as Slave

units). The Remote Terminal Unit (RTU) connected to the TC2401 will respond only to the poll with that

RTU's own specified ID (or address), which is embedded in the poll message. The communication between

the Master and Slave is transparent to protocol and data rate; transmission can be full duplex provided only

one RTU responds at a time.

The dual ring consists of an "A-Ring" and a "B-Ring." The A-Ring is the primary fiber optic ring and the B-

Ring is the backup fiber optic ring. Each Slave unit can detect any one of four possible cable breakage

conditions, referred to as "fault conditions," as shown in Figure 4. The TC2400/2401 can detect ring

breakage on either the A-Ring or B-Ring. When a cable breakage occurs, both the upstream TC2401 and

downstream TC2401 can detect the breakage and "wrap" around the data accordingly, as shown in Figure

The TC2400 and TC2401's panels are equipped with multiple LED indicators and DIP switches. The LEDs

indicate data wrap or fault conditions such as "A2B" (or Loop A to B), "B2A" (or Loop B to A), or optic

signal loss. The DIP switches can activate the "Local Loopback" function or generate a pulsed electrical

signal to simulate a broadcast signal from the SCADA host. These features can be very useful during

installation or when troubleshooting the system. A dry contact relay alarm can be utilized to provided

alarm status to the local RTU. In the event that self-healing occurs, the local RTU can relay the alarm

condition back to the SCADA host controller, enabling the operator to easily determine and locate the

problem site(s).

The electrical interface for the TC2400/2401 can be RS-232, RS-422, or RS-485 (2 or 4 wire). Typical

applications include SCADA, process control, traffic control, and energy management. Due to the Self-

Healing capability, the TC2400/2401 can provide maximum reliability for crucial SCADA applications.

Chapter 1 - Overview

Figure 1. Self-Healing Ring Topology

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TC2400 & TC2401

Ring User's Manual

Rev. 1.7

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Tc2401