I just had my house phone connected and it's wired through conduit in the wall, so everything looks as professional as possible. Unfortunately the phone company here in Mexico does not connect phone jacks that are not their property. So I’m basically stuck doing it myself.

They have a 2 wire (blue and white) cable to their phone jack and my jack has 4 places I can connect to but cant figure out which two to use (TX,L2,TS,L1)

  • 1
    Phone wiring is pretty standard, he's got an RJ-11 modular jack being interfaced to a T-568A single twisted pair. Commented Mar 22, 2015 at 3:27

1 Answer 1


L1, L2 cross-references to TIP and RING respectively per standard US phone nomenclature. TX/TS can be wired as the second line TIP2/TX, RING2/TS or a sort of daisy chain, but in a single line system, can be ignored.

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Wiring on this will be

  1. Green => Tip => L1
  2. Red => Ring => L2

This pair will connect to the center pair of contacts in the modular socket/jack. Most phone wall cords sold are RJ-11 with a single pair to save money.

What the phone company has given you is a standard T-568A (Cat 4 or 5) color coded single pair. If you examine it closely, one wire's insulation will be white with blue stripe and the other will be solid blue.

It cross-references to the old RING/L1, TIP/L2 wiring convention as follows:

  1. White/Blue => Green => Tip => L1
  2. Blue => Red => Ring => L2

RJ Modular wiring:

  1. RJ-11 Single Pair
  2. RJ-14 Two Pair
  3. RJ-25 Three Pair

POTS Local Loop voltages (positive ground to reduce electrolytic corrosion):

  1. Tip is at ground potential
  2. Ring is -48V DC (nominal)
  • 1
    AKA, the middle two, using blue and blue w/ stripe. Reverse them if it doesn't work.
    – Mazura
    Commented Mar 22, 2015 at 4:33
  • Trivia: "tip" and "ring" do indeed take their names from how they were connected to phone plugs, back in the days when switchboard connections were made manually by the operators.
    – keshlam
    Commented Mar 22, 2015 at 5:34
  • 2
    With only 2 wires, the easiest way to figure out what wire is attached to what is with a multimeter. You should get 50-60v DC across the two wires. If it reads postive voltage, the wire going to red lead on the multimeter is L1 and the other one is L2. If it reads negative voltage, the wire going to the red lead is L2.
    – Comintern
    Commented Mar 22, 2015 at 15:30

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