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Question about RJ11 to RJ45 DSL cable [Solved]

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larry77
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Question about RJ11 to RJ45 DSL cable [Solved]

#1 Post by larry77 »

Dear All,
I need to buy a DSL cable (RJ11 to RJ45, from phone socket to Fritz 7530 router).
My only question is the following (BTW, I am not an expert at all): if I look on Amazon or somewhere else online for RJ45 cables (RJ45 on both sides), the seller always indicates the category (5, 6, etc...) of the cable so you know the data flows it can sustain.
However, when I look for RJ11 to RJ45 cables, I never get this kind of information. Are those cables all the same or is there any parameter I should look at?
Thanks a lot!
Last edited by larry77 on 2022-08-04 09:05, edited 1 time in total.

steve_v
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Re: Question about RJ11 to RJ45 DSL cable

#2 Post by steve_v »

larry77 wrote: 2022-06-26 12:07I need to buy a DSL cable (RJ11 to RJ45, from phone socket to Fritz 7530 router).
Presumably by "DSL cable" you mean "plain old telephone cable with 6p4c RJ11 (or BT) on one end and whatever your router manufacturer pulled out their ass on the other"?

DSL runs over POTS (plain old telephone system) cables and is extremely tolerant (of 1930s wiring, interference, and all the crosstalk and other crap on the phone lines) by design. Therefore the only questions that really need answered about your pre-made cable are: a) Does it have enough (2) wires in it, and b) are they connected to the correct (center 2 IIRC) pins of the correct connectors. YMMV WRT telephone wiring standards depending on where you live in the world of course.

Do check that DSL port is really RJ45 before you buy anything though. RJ[X] is a telephone wiring standard not a connector type so I suggest counting pins, and I suspect you will find there are 4 or 6 rather than the usual 8 in an ethernet cable.
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Re: Question about RJ11 to RJ45 DSL cable

#3 Post by NFT5 »

larry77 wrote: 2022-06-26 12:07 Are those cables all the same or is there any parameter I should look at?
Although steve-v is correct in saying that, so long as the connector is the correct one, i.e. RJ11 or RJ45 and that the wires are connected to the right pins, it will work, that's not necessarily the whole story.

A lot of cables terminated in RJ11 are made to an absolute minimum standard, i.e. how cheap can it be made and still work. If it's just for a telephone then that doesn't really matter. But, for data, especially when there's lots of it, quality does play a big role in the performance you'll get.

For example, I have a cable connection (VDSL, not ADSL over a phone line) from my ISP. It's capable of Gigabit speeds but I pay for 100Mbps. When first connected we were only getting around 50Mbps, so I complained. The nice lady on the help desk asked if I had another RJ11 terminated cable to connect from the wall socket to the modem. Like any self-respecting semi-nerd I had a whole bag full of them. Trying different ones resulted in an immediate improvement of over 10Mbps, so I was getting over 60Mbps. She then organised a technician to visit. He took one look and went about 100m down the street to the junction box and when he came back we had 120Mbps. Apparently all he did was disconnect and reconnect to a different, better quality line.

Length of cable makes a difference, too. Even though our connection is at one end of the house we were strongly advised to keep the connection from the wall to the modem as short as possible. I tested this in my shop and a 15m cable (good quality) resulted in a performance degradation of around 15Mbps.

So, the lesson is to use the best quality cable you can get and keep it as short as you can. Unfortunately price isn't always a direct indicator of quality.

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Re: Question about RJ11 to RJ45 DSL cable

#4 Post by larry77 »

Thanks a lot.
Perhaps the simplest thing to do is to buy this

https://www.amazon.de/-/en/gp/product/B01LY5CQVM?psc=1

and forget all the rest.
I will give it a shot and come back if I have problems.

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Re: Question about RJ11 to RJ45 DSL cable

#5 Post by reinob »

I think something like: https://www.amazon.de/deleyCON-Telefonk ... B09NM9H1WQ

will suit you just fine, as the adapter you posted will (unnecessarily) add a further connection, so you will have RJ11-RJ45(male)-RJ45(female)-Router, which may or may not affect the maximum speed you can get (ADSL and VDSL are very fussy about length and multiple legs, etc.).

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Re: Question about RJ11 to RJ45 DSL cable

#6 Post by larry77 »

Indeed this is what I did. I suppose there was a lack of understanding on my side. I do not have a fiber connection, but one going through the phone, so the type of phone cable plays a less important role.

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