Wire Gauge and Resistance

Last Updated on Fri, 30 Jun 2023 | Telecommunications

Most telephone cable installed since 1980 is either 24 AWG or 26 AWG. 26-gauge wire has a slightly smaller diameter than 24-gauge, and many more pairs can be placed in the same space required by 24-gauge wire. (The international equivalent diameters are 0.5 and 0.4 mm.) Before 1970, and especially before 1960, 22-gauge wire was often used. In the 1950s, 19-gauge wire was occasionally installed. The difference between DC loop resistance on an 18,000-foot pair of 19-gauge wire and 26-gauge wire is radical. Smaller wire gauges became popular as lower loop currents were required to obtain acceptable telephone performance, and as the need for many more wire pairs in the cables and conduits developed.

A quick comparison of DC resistance further illustrates the difference between 24- and 26-gauge wire: 24-gauge wire has a resistance of 26 Ohms per 1000 feet, and 26-gauge wire has a resistance of 41 Ohms per 1000 feet, measured at a temperature of 25C/75F. A telephone line is a DC loop, so 18,000 feet of cable is actually a loop of 36,000 feet of copper wire. A significant change in resistance occurs from cool to hot ambient temperature, especially when using aerial cable that is exposed to the sun. Therefore, DSL performance can change between midnight and noon in some climates, simply because of increased resistance that causes increased attenuation as the cable heats between midnight and noon. Recall that as resistance (and correlative attenuation) increases, SNRs degrade.

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Readers' Questions

  • KEEGAN
    How to wire phone line?
    1 month ago
    1. Unplug all phones and equipment from the telephone line.
    2. Locate the cable input jack on the wall.
    3. Disconnect the phone line from the wall jack.
    4. Cut the end of the phone cord and strip back the outer insulation and the two internal wires.
    5. Connect the red wire of the phone cord to the red screw on the phone jack and the green wire to the green screw.
    6. Tighten the screws to secure the wires; then attach the phone line cord to the wall jack.
    7. Plug in the telephone or other device and test the line.
    • frank
      Is 22 gauge smaller than 24?
      1 month ago
      • No, in terms of wire gauge, a 22 gauge wire is larger than a 24 gauge wire. As the gauge number increases, the wire diameter decreases.
      • fatima
        What gauge is telephone wire?
        1 month ago
        • The gauge of telephone wire typically used in residential or commercial installations is commonly 24 or 26 AWG (American Wire Gauge).
        • Salvatore
          What cable is used for phone lines?
          2 months ago
          • Most telephone services use a four-conductor cable to carry both audio and signaling between the telephone and the central office or between two pieces of phone equipment. This type of telephone cable is commonly known as RJ-11 or RJ-14 cable, which contains four wires.
          • sofia
            How much resistance should a wire have?
            7 months ago
            • The resistance of a wire is determined by its electrical resistance, which is affected by many factors, including the material, length, and diameter of the wire. Therefore, it is not possible to provide a single, definitive answer to this question.
            • HAZEL
              What are the different gauges of wire?
              7 months ago
              • The most common gauges of wire are: - AWG (American Wire Gauge): This is the standard in most countries and is used for anything from appliance wiring to automotive, home, and commercial applications. - SWG (Standard Wire Gauge): This is the British standard for electrical wire and is used primarily in the UK. - Metric (mm2 or sq mm): This system is used in many countries, including Australia, and is the metric equivalent of AWG. - B&S (Brown & Sharpe): This is an American system used in the electrical industry, primarily for automotive and industrial applications.