# Carrier line-matching-unit interface

Canonical URL: https://eloragrid.ai/symbols/carrier-line-matching-unit-interface
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: CLI
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchyards
Input: Carrier terminal circuit
Output: Matched coupling interface

Identifies the matching boundary between the carrier terminal path and the primary coupling equipment.

## In plain English

### What this block does

Identifies the matching boundary between the carrier terminal path and the primary coupling equipment.

### A simple example

In a switchyard line bay, carrier-coupling equipment can connect a protection communication terminal to the transmission conductor. Fiber-based protection uses another physical path but still needs named endpoints and channel supervision. For this reference, the drawing identifies “Carrier terminal circuit” at the input and “Matched coupling interface” at the output. Matching and protective functions are equipment-specific.

### What the drawings help you do

Start at the named input: Carrier terminal circuit. Identify its source device or document and the state represented on the drawing. Follow the named output: Matched coupling interface. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Carrier terminal circuit
- Output: Matched coupling interface
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Carrier terminal circuit → CLI → Matched coupling interface
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Line traps: power-line carrier communication](https://www.gevernova.com/grid-solutions/sites/default/files/2025-09/Line-Traps-Brochure-EN-N50059-Hybrid-202504-R002.pdf)


## What it represents

Identifies the matching boundary between the carrier terminal path and the primary coupling equipment. A protection communication interface carries information between circuit ends or couples a communication signal to a primary line. Its signal path is different from the power-current path even when both use part of the same installation.
In a switchyard line bay, carrier-coupling equipment can connect a protection communication terminal to the transmission conductor. Fiber-based protection uses another physical path but still needs named endpoints and channel supervision. For this reference, the drawing identifies “Carrier terminal circuit” at the input and “Matched coupling interface” at the output. Matching and protective functions are equipment-specific.
Show each coupling boundary and the intended information direction. Frequency selection, channel performance, insulation duty and protective coordination require the selected communication and primary equipment design. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.

## How to read it

- Start at the named input: Carrier terminal circuit. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Matched coupling interface. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Matching and protective functions are equipment-specific.
- Show each coupling boundary and the intended information direction. Frequency selection, channel performance, insulation duty and protective coordination require the selected communication and primary equipment design.

## Information to show or reference

- Label the source and connection reference for carrier terminal circuit.
- Identify the destination and defined state of matched coupling interface.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Matching and protective functions are equipment-specific.

## Important distinction

Matching and protective functions are equipment-specific. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

## Facts

- Representation: Functional block
- Installation focus: Switchyards
- Input / boundary: Carrier terminal circuit
- Output / connection: Matched coupling interface
- Lookup label: CLI is a library lookup label, not a standard device designation.

## Public references

- [Line traps: power-line carrier communication](https://www.gevernova.com/grid-solutions/sites/default/files/2025-09/Line-Traps-Brochure-EN-N50059-Hybrid-202504-R002.pdf) — GE Vernova. Public technical context for line carrier and protection communication interfaces. Line traps, coupling and power-line carrier communications. The application text and educational graphic are independently authored; the publisher does not certify this representation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.