If I install 20meters of ethernet unshielded utp wire (rj-45) together with a phone twisted pair wire (rj-11), one touching the other, will create interferences between them?

2 Answers 2


No, it is extremely unlikely. This is done everywhere. It is very common to use the "unused" pairs in typical 10-Base T ethernet connections for either traditional analog or even digital phone service. The construction of "category" ethernet cable has precision twisting of the four pairs exactly to minimize any crosstalk between the ethernet and the telephone signals.

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    On top of this, the phone signal is something like 0-20 kHz, while the Ethernet signal is probably something like 1-100 MHz (no DC content due to encoding).
    – The Photon
    Dec 23, 2016 at 17:16

Shouldn't be a problem generally speaking. The ethernet carries digital signals on the wires and the two-pair POTS wires carry analog signals. If crosstalk or other interference did occur I think it would most likely be during ringing of the phone, when current was being drawn through the wire to ring the phone(s).

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