Allied Encyclopedia – What Do the Letters on Portable Cord Mean?

Allied Encyclopedia

Everyone uses extension cords, from contractors with power tools on major build sites to families powering their holiday lights. With all the seasonal decorations going up using more and more extension cords, we thought it might be worthwhile to define those pesky letters found on some portable cord packaging and on cable manufacturer websites.

The same rules apply to extension cords that apply to any other cable: voltage ratings, temperature ranges, environmental resistances, etc. On the packaging of some portable cords (and on all the portable cords on our website as well) you’ll see a set of letters, up to 4 letters long. These letters connote the set of ratings applicable to the cord.

  • S – Service, which means the portable cord has been rated for 600 volts.
  • J – Junior. Junior is short for Junior Service, which means the portable cord has been rated to 300 volts.
  • T – Thermoplastic. This refers to the material the cord jacket is made out of. Click here to learn more about Thermoplastic material. Thermoplastic material is light-duty and can be used as consumer grade portable cord.
  • E – Elastomer, which is short for Thermoplastic Elastomer. It also refers to the jacket material but it is different from plain Thermoplastic. Thermoplastic elastomer material is medium-duty and performs better in colder temperatures than thermoplastic. If a portable cord does not have a ‘T’ or an ‘E’, it is made of thermoset material, which makes it heavy-duty.
  • O – Oil Resistant, and the single ‘O’ means that only the outer jacket is oil resistant.
  • OO – Also Oil Resistant, but this time both the portable cord’s outer jacket and the insulation are oil resistant.
  • F – Fixture Wire, which means the cable is rated to 90°C.
  • P – Parallel. This cable is parallel-jacketed and is sometimes called “zip cord.”
  • H – Heater cord. This is used in UL cord types such as HSJ, HS, HSO, and HSJO.
  • V – Vacuum cord. “V” is the UL marking in parts like SVT and SVO. This is light-duty portable cord.
  • RD – Range or dryer cord. Product examples include SRD, SRDE, and SRDT cord.
  • W – Weather Resistant. Portable cord with a W means it’s approved as weather (sunlight, moisture, etc.) and water-resistant and can be used indoors or outdoors.

So the next time you’re in the market for some portable cordage either from a manufacturer/distributor or from your local hardware store, you’ll be armed with the right information to make the correct choice for your needs!

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Phoenix, AZ; Bedford, NH; Pewaukee, WI; Rochester, NY, Tampa, FL; and Mt. Juliet, TN. For more information on Allied, visit our main website at

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