I am doing some rewiring of our internal phone lines (almost entirely removal of unused lines). The issues we have run into is the router will every now and then simply not connect from the house to our provider.

The wire from the NID to the router is an old, very thin 4 wire phone cable (GRBY wires). I am going to replace it whether it is the culprit or not. The outer sheath is getting brittle.

The plan is to use an outdoor UV gel filled Cat5e to go from the NID to inside the house, then Cat5e from a box there to the router (or maybe just gel filled all the way, it's a fairly wet basement). This is an old house and the cable will run near and across many power cables.

Given the possible interference would it be worth it to double up cables from the NID to the router (i.e. use blue/blwh together for ring and orange/orwh together for tip)?

I'm not exactly clear how the twists work with data communication so maybe it would be better to use blue/orange and blwh/orwh instead?

Would this even help with possible interference or signal strength?

  • \$\begingroup\$ no, that sounds like it would be worse; the pairs are designed to eliminate crosstalk. if you take away the pairing, it would get worse. use cat6 if in doubt: it separates the pairs with a small plastic crossbar. \$\endgroup\$ – dandavis Aug 28 '17 at 19:37
  • \$\begingroup\$ crosstalk with what? there is nothing else on this wire. 6 of the 8 wires would be disconnected with only one dsl line. If there is an issue with how the twists are designed I also asked about using them paired blue/orange for ring, blwh/orwh for tip if that's what you are talking about. \$\endgroup\$ – Simurr Aug 28 '17 at 20:09

Given the possible interference would it be worth it to double up cables from the NID to the router (i.e. use blue/blwh together for ring and orange/orwh together for tip)?


Besides what asndre said, which is true, if you put two transmission lines in parallel, the following occurs:

  • Impedance is halved, so it will be mismatched.

  • Since one line will always be a little bit longer than the other, the signal at the end will be the sum of both, therefore it will include two copies of the original signal, summed with a slight delay, which will degrade signal integrity.

In other words, use good quality outdoors-proof waterproof twisted pair telephone cable, with the same impedance as the original phone cable. It'll work fine. The less connection boxes on the way, the better.

If you think you might someday need to put a connection box somewhere on the cable, simply reserve a meter extra cable at this point, coiled. If you use conduits (you should) then keep a bit of extra of cable at the end that you can pull through the conduit if you need to cut it in the middle to install an extra connection box.


It is very bad idea to use Cat5e-based wiring/cabling to establish a xDSL connection.

Cat5e wiring is not designed for so low frequencies and therefore does not feature an appropriate characteristic impedance (i.e. Z(f)) at the frequencies employed by xDSL which works in telephone line bandwidth (<20 kHz).

Using Cat5e for xDSL also results in dramatical signal attenuation, about 3~5 times worser comparing with an appropriate cable/wire.

To be short, POTN is about 600-Ohm techniques while Cat5e if for 100-Ohm ones.

  • \$\begingroup\$ How do you figure? Copper is copper and the wire gauge is the same as Cat3. This was going over old untwisted 4 wire cable that was also 24AWG. \$\endgroup\$ – Simurr Nov 9 '17 at 22:29
  • \$\begingroup\$ @Simurr Cat5e is not specified for so low frequencies. For example, G.SHDSL works in 0-400 kHz bandwidth at 2 Mbps and 0-125 kHz at 640 kbps. Cat5e is specified beginning from 1 MHz. \$\endgroup\$ – asndre Nov 10 '17 at 18:59
  • \$\begingroup\$ @Simurr Copper as material and wire gauge as square dimension define the DC resistance on the cable. But is this the only parameter significant for proper transmission? What about characteristic impedance, Z(f), which defines the cable AC characteristics significant for transmission? \$\endgroup\$ – asndre Nov 10 '17 at 19:02
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    \$\begingroup\$ I do an awful LOT of audio and Production Intercom for Live broadcast events. My standard disposable long-run interconnect cable is cat-5. I will often use 30 or 40 boxes of cat-5 cable. I simply treat the cable as 4 very high quality twisted pairs. And it works incredibly well. \$\endgroup\$ – Dwayne Reid Dec 29 '18 at 21:19
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    \$\begingroup\$ @asndre: distances range from perhaps 100m to 700m or more (300' - 2500'). Baseband audio. BUT I have also done ADSL modems at the end of long runs of a single pair of cat-5 cable. No issues at all. \$\endgroup\$ – Dwayne Reid Dec 30 '18 at 16:27

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