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Clarification of Communication Circuit Definition

Question asked by dan.pohnert on Oct 13, 2017
Latest reply on Dec 15, 2017 by nealxu

"800.2 Definitions.

Communications Circuit.

The circuit that extends voice, audio, video, data, interactive services, telegraph (except radio), outside wiring for fire alarm and burglar alarm from the communications utility to the customer's communications equipment up to and including terminal equipment such as a telephone, fax machine, or answering machine."

"90.2(B) Not Covered.

Informational Note to (4) and (5): Examples of utilities may include those entities that are typically designated or recognized by governmental law or regulation by public service/utility commissions and that install, operate, and maintain electric supply (such as generation, transmission, or distribution systems) or communications systems (such as telephone, CATV, Internet, satellite, or data services). "

"725.121 Power Sources for Class 2 and Class 3 Circuits.

725.121(A) Power Source.

(4) Listed audio/video information technology (computer), communications, and industrial equipment limited-power circuits.

Informational Note: One way to determine applicable requirements for listing of information technology (computer) equipment is to refer to UL 60950-1-2011, Standard for Safety of Information Technology Equipment. Another way to determine applicable requirements for listing of audio/video, information and communication technology equipment is to refer to UL 62368-1-2014, Safety of audio/video, information and communication technology equipment. Typically such circuits are used to interconnect data circuits for the purpose of exchanging information data. One way to determine applicable requirements for listing of industrial equipment is to refer to UL 61010-2-201, Safety requirements for electrical equipment for measurement, control, and laboratory use –Part 2-201: Particular requirements for control equipment, and/or UL 61800-5-1, Adjustable speed electrical power drive systems –Part 5-1: Safety requirements –Electrical, thermal and energy. "


There is a excessive amount of confusion on what constitutes a "communication circuit". There are several schools of thought:

1)  A communication circuit extends the analog telephone circuits from the utility demark point of connection so only cables connected to the utility demark directly are communication circuits. Placing any PBX or equipment between the terminal equipment makes it no longer a communication circuit and this now falls under Article 725.

2) Only analog telephones  circuit including PBX and internal connection from that PBX to terminal equipment. Network copper Ethernet cables fall under Article 725. Since analog PBX is not listed to UL 60950 or 62368 then it is not under Article 725

3) Since the communication utility includes internet and data service as communication utility (per 90.2 B) and the it is the extension of data in the definition all analog voice and Ethernet cables thus all copper structured cabling inside a building customer owned is a communication circuit.

The reality is that in real world applications the same port and cable can be used for voice or data depending on which piece of equipment (PBX, analog voice path panel or network switch) the owner connects the outlet via patch cords in the comm. room this can occur any time during the life of the installation.

Article 725 and 800 claim audio, video, data and communication. Which is the correct interpretation?

There is also the ever popular composite cable argument

"725.139(D)(2) Composite Cables.

Cables constructed of individually listed Class 2, Class 3, and communications cables under a common jacket shall be permitted to be classified as communications cables. The fire resistance rating of the composite cable shall be determined by the performance of the composite cable."

It is kind of muddy