How to Read Cable Jackets

When it comes to the world of cables, there’s more than meets the eye. While most consumers focus on the electrical properties and applications of a cable, there’s an often overlooked component that plays a crucial role in the cable’s functionality and safety: the cable jacket. This protective layer, which insulates the cable, carries a wealth of information about the cable’s properties and potential applications. In this article, we’ll delve into the details of how to read cable jackets and why this knowledge is essential for both consumers and professionals alike.

The Importance of Cable Jackets

Cable jackets serve a dual purpose. Not only do they protect the internal components of the cable, but they also provide valuable information about the cable’s properties. This information, printed directly on the jacket, can include the manufacturer or UPC code, jacket material, any electrical standards it meets, temperature rating, and a material rating that tells you where the cable can be run in a building. Understanding these details can help ensure that you select the right cable for your specific needs.

Deciphering the Information on Cable Jackets

Let’s take a closer look at the types of information you might find on a cable jacket and what each piece of information signifies.

Manufacturer and Product Name

The manufacturer’s name and product name are usually printed on the cable jacket. This information can be helpful if you need to reorder the cable or if you have questions about its use. For example, if you see “Belden” and “10GXW12” printed on your cable jacket, you know that the cable was produced by Belden and the specific product is the 10GXW12 cable.

Number of Pairs and Diameter/AWG

The number of pairs in the cable is often indicated with “4PR,” “2PR,” etc. This tells you how many pairs of wires are inside the cable. Next to the number of pairs, you’ll find a two-digit number representing the American wire gauge (AWG) or the cross-sectional area of a round wire (essentially the diameter). The larger the number, the smaller the cable’s overall diameter, which can affect how easy the cable is to manage and install.

UL Reference Number and UL Marking

The UL reference number is a unique identifier for the UL filing number, which varies for different designs and manufacturers. The UL marking, which stands for “Underwriters Laboratories,” indicates that the product has been approved by this global safety certification company. The UL marking applies to products designed and sold within the United States, while the “cUL” marking applies to products designed and sold within Canada.

Material Class/Fire Rating

The material class or fire rating tells you where the cable can be used in accordance with the National Electrical Code (NEC or NFPA 70). For example, “CM” indicates a general-purpose cable, while “CMR” tells you that the cable is riser-rated, designed to prevent fire from spreading from floor to floor. “CMP” indicates a plenum-rated cable that restricts flame spread to no more than 5 ft.

Temperature Rating

The temperature rating, such as 90 degrees C, indicates the maximum ambient temperature at which the cable jacketing will maintain its fire rating properties. If the ambient temperature exceeds this rating, the materials may start to degrade, potentially impacting cable performance.

Category and RoHS

On a copper cable, you’ll see “CAT 5E,” “CAT 6,” “CAT 6A,” etc. This tells you what type of cable it is and what type of bandwidth to expect—and across how many meters. The RoHS acronym indicates that the cable’s manufacturer followed the Restriction of Hazardous Substances (RoHS) guidelines, which restrict the use of hazardous materials found in electrical and electronic products.

The Role of Cable Jackets in Different Applications

Cable jackets play a crucial role in various applications, from home use to commercial server rooms. For instance, if you’re running a Cat5 cable in your home, the cable jacket’s information can help you determine if the cable is suitable for your needs. Similarly, if you’re running a coaxial cable in your living room or alongside your power cables, the cable jacket can provide insights into whether the cable has the appropriate shielding to prevent electrical interference.

In commercial settings, such as server rooms, the information on the cable jacket can be even more critical. For example, the fire rating can help ensure that the cable meets the necessary safety standards for the building. Similarly, the temperature rating can help ensure that the cable can withstand the ambient temperatures in the server room without degrading.


Understanding how to read cable jackets is a valuable skill for anyone dealing with cables, whether you’re a consumer setting up a home network or a professional installing cables in a commercial building. By taking the time to understand the information printed on the cable jacket, you can ensure that you’re using the right cable for your specific needs, enhancing the safety and efficiency of your cable applications.

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