VOIP Phone: RJ11 - SFP module?

I’ve moved to an ISP that provides a VOIP landline, but alas their staff (as is the case with all low end, cheap ISPs I figure) are clueless if you’re not using their “approved” router, which is a Huawei HG659. It has an RJ11 pot on back and presumably some VOIP configs on it web interface that this ISP exploits.

The Omnia lacks an RJ11 port, but it does have a SFP module cage, and approved SFP modules:


(none of which are listed as RJ11 copper based, for VOIP).

I guess I’m curious:

  1. Is there an SFP module availablet hat ads an RJ11 port for VOIP use>
  2. Can Turris OS (OpenWRT) be configured (easily though Foris or Luci) or more basically (with UCI or simply the filesystem configs) to dedicate one of it’s ports (either an SFP provided one or one of it’s other RJ45 ports) to a VOIP connection?
    • If so, can a simple RJ11 phone plug into one of those ports, perhaps with a small adapter?

Here’s a classic cheap little plug converter:

for example and here’s a generic GB RJ456 SFP:

Wondering if anyone has experience or advice here? Both those are cheap enough to take a punt on, but still, any a-priori advice/experience is welcome,

Ask your ISP on which VLAN they advertise VoIP and what are the credentials to connect, buy IP-phone that has RJ45 connector. And use one of the LAN port configured to that VLAN and it should work.

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Here is a little more info on RJ11:

You likely need an ATA Device, here is one user’s story of their rotary phone:

Or even, depending on your technical ability, there are FreeSwitch packages available from OpenWRT:

The answer is easy, no that device does not exist. VoIP, or voice over IP typically does not use RJ11 modular connectors… RJ11 was/is traditionally used for analog POTS (plain old telephony system) to connect phones to the socket (but e.g. in Germany and the UK, telephone sockets do not use RJ11 connectors at all).
All-in-one routers with a RJ11 port typically either use this to connect to the phone line (e.g. for DSL or to access an analog POTS band) or more often allow to connect an old analog phone to the router’s VoIP basestation. You can buy dedicated converter devices that convert analog phones with VoIP (these are essentially small stand-alone VoIP base stations). One way to get a chep VoIP base station that might even allow analog phones is to get a second hand Fritzbox and configure it to use one of its LAN ports as WAN and then connect it to your turris router. Fritzboxen in some markets come with ready-made configurations for some of the ISPs so getting this to work might be as simple as selection the correct ISP from a drop down list and potentially adding VoIP user name and password.

No can do, these RJ45 ports talk “ethernet” so you need to connect a device that also talks ethernet, which analog phones/fax-machines decidedly do not… but you can connect a VoIP basestartin or ATA converter as these typically speak ethernet as well.

You can make that work physically but it will never work on the electric/signal side:
a) gigabit ethernet uses all 4 pairs of a CatX cable, while RJ11 (6P2C) only has at most 6 contacts (but RJ11 only uses two of these)
b) analog phones do not actually talk ethernet and typically expect something like 60Volt on the phone line to work at all, something that ethernet does not deliver (with power over ethernet you can deliver power, but not in an analog phone compatible way).

So you best start looking for a stand alone VoIP base station.

Which ISP and which country are we talking about? Often googling can help to figure out how to configure VoIP for different non-cooperating ISPs…
(Case in point my ISP O2/telefonica is generally open with VoIP credentials but requires that one uses O2’s DNS servers otherwise the SIP server names do not resolve).