Advice on running POTS over ethernet cabling

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nicks

126 posts

Master Geek

#319913 13-Jun-2025 18:26

Apologies in advance if my terminology is wrong, or if this has been answered and my searches have missed it.

My in-laws have moved into a new(ish) house that has data cabling throughout, terminating in a data cupboard in the garage which also houses the ONT. Rightly or wrongly they have a landline phone which they want to keep. It is currently connected to the RJ11 (?) POTS port on the ONT and working fine. However, I would like to use the patch panel to connect one of the ethernet ports in the living room to the POTS port on the ONT so they can have their phone there.

Google suggests it's possible with the use of an adaptor, but I am not sure exactly what I need to get. I have done a few searches in PB Tech, Jaycar etc but can't find anything obvious (to me).

Can anyone offer some guidance?

Cheers, Nick.

RunningMan

8965 posts

Uber Geek

#3383750 13-Jun-2025 18:31

One of these at each end should do it https://www.pbtech.co.nz/product/CABDNX0091/Dynamix-C-RJ1245-2-4C-RJ12-to-RJ45-Cable---2m---Gr

JemS

48 posts

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#3383751 13-Jun-2025 18:34

We have the exact same situation in our house and we have just plugged the rj12 straight in the rj45 port. Haven't had any issues for 10+ years.

richms

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#3383752 13-Jun-2025 18:35

Some people say that it will ruin the RJ45 to plug it straight in. I have not found that but I have found that it doesn't sit nicely in the socket and can twist and lose connection easily.

Richard rich.ms

RunningMan

8965 posts

Uber Geek

#3383757 13-Jun-2025 19:08

JemS:

We have the exact same situation in our house and we have just plugged the rj12 straight in the rj45 port. Haven't had any issues for 10+ years.

As @richms says, this can cause issues. It will work fine with an RJ12 plugged in but the problem comes when you unplug the RJ12 and plug an RJ45 back in and the outer pins may be bent slightly out of shape and make poor contact.

froob

692 posts

Ultimate Geek

Lifetime subscriber

#3383769 13-Jun-2025 20:05

If you need to plug in more than one phone, you can also use an adapter like this one: https://www.pbtech.co.nz/product/ADPDNX1023/Dynamix-C-RJ45DS-4B-RJ45-Splitter-Bridged-All-Pins?srsltid=AfmBOopUsUEGm-Tyv4twou01kjhE24Quo3JsZ9aY9xK1NHqxcuVksoAo

You would use one of the cables linked above to connect the adapter to the ONT, then standard ethernet patch cables from the adapter to the relevant ports on the patch panel. Then, again using the cable above to connect each phone to the wall socket.

Guide: Installing Network Cabling in New Zealand Homes

nztim

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TEAMnetwork

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#3383859 14-Jun-2025 10:59

JemS:

We have the exact same situation in our house and we have just plugged the rj12 straight in the rj45 port. Haven't had any issues for 10+ years.

NEVER do this, it will damage pins 1.2.7,8 in the socket and will never work for data again in the future

Any views expressed on these forums are my own and don't necessarily reflect those of my employer.

BarTender

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#3384140 14-Jun-2025 20:52

I have some RJ11 to RJ45 cables from a telephone system I decommissioned under my house. If you’re in Wellington you are welcome to 3 or more of them. Or just get some RJ11 to RJ45 cables off AliExpress.