Fritz!Box 7590 - and how to connect it


Staff member
I have FTTC (Fibre broadband to cabinet) service plus landline, currently from PlusNet. Up to press I have been using the supplied router which I have never been totally happy with. So I have been passively contemplating replacing it for a while. WiFi coverage was fine for my property as was line speed. But a few times a month, I would awake to find it had disconnected (with no indication of same on the router itself) and needed restarting. No big deal in itself. But I recently installed a Tado Smart boiler control kit and that is reliant on a continued internet connection for the scheduled changes to occur. And I found myself waking to an unheated home every few days - the web connection was down again and a router restart needed. I did contemplate putting a mains timer switch on it to restart it daily in the small hours, but eventually decided to bite the bullet and get a new modem/router combo. The question is - which?

With some spare funds available (due to Covid lack of lunches out and holidays etc.) I decided on the top-of-the-range Fritz!Box 7590. UK spec version, from Amazon.
Amazon product

Brief review

It has been in place for ten days and has been flawless (*). My internet line speeds are marginally higher; the connection has not (yet) dropped and WiFi coverage is pretty much the same as the supplied Hub.

It's highly configurable and it DOES need some manual settings to be applied to get it to connect to PlusNet. The required values are on PN's site. So that was fairly painless - but not simply plug and go. It contains a setting (on by default) whereby it automatically disconnects and reconnects itself at a time of your choosing (in my case ~3am) which may well account for the connection reliability. The browser interface is comprehensive and contains many settings and diagnostic tools for the "expert" user. As well as your main WiFi SSID, you can configure alternate "guest" access, with limitations of your choosing on the level of access they have.

So - as a modem/router for DSL - it's an excellent (if not expensive) piece of kit and on that basis only, after 10 days of use, I'd have no hesitation in recommending it.

But it does more. Alongside its internet use, it also acts as a DECT base station that can be connected to any of: analog landline; SIP (VOIP); ISDN. At present I only have an analog landline service, but I am future proofed if I choose to go SIP at some point. Combining router and DECT in this way gives advantages: if you want additional SIP phone services, it will combine these with analog service into the same unit; and there is a free App for Android/iOS which allows such a device connected via WiFi to act as a "DECT" handset - you can make and receive landline calls on your mobile. You can access the box's web interface remotely as well, meaning you can view your calls history and so on even if away from home. It has an inbuilt answermachine and can be used to record calls. It works fine with some ~15 year old DECT handsets; for best function, a dedicated Fritz! handset is also available.

It also has two outlets on it for wired analog handsets. These (if used) work alongside DECT handsets to make a kind of switchboard; internal calls can be made as well as external.

If you do have more than one phone service (2+ SIPs or 1+ SIP plus analog) you can call into the box from anywhere and then dial back out on a different line, thus "spoofing" your real location and/or using whichever tariff your outgoing line applies.

It would certainly make a sound basis for a very small business's telephony and is easily comprehensive enough for a domestic setting. I am very impressed.

Flawless (*)??
One thing is missing. Fritz! have chosen to use a single socket on the box (it's a dual RJ45/RJ11 port) for BOTH internet and phone services. In the UK such services are typically delivered via either a standard BT phone socket - in which case a DSL splitter is needed - or through a new faceplate with a DSL splitter inside. Either way, you need to feed Fritz! with the two signals at separate pins on that input port. It does NOT have a splitter onboard. And they do not provide a cable to do this, nor proper instructions as to how to connect it for both web and telephony. The supplied cables and adaptors are of no use.

So initially I wasn't able to use the telephony part of it. I just connected the DSL side using the same cable as I had used with the old router. Fritz! support did offer to send a cable for free, but the only one they have is terminated in RJ45s on all three ends and with UK standard socketry, we need a RJ11 for web and a BT for analog phone. I have seen cables on sale on EBay for the UK market but in the event, I decided to make my own. I did so by cutting three cables with the right "ends" already attached and joining the cut ends (solder, shrink-wrap) to complete.

How to connect it

In case anyone else is in the same situation, by much trial and error (complicated somewhat by not having someone "tame" I could call repeatedly for them to evaluate call quality at the "far end") I have established the required wiring scheme for DSL plus analog phone line as follows:

I am not referring here to any colour code conventions for cable cores; these seem to vary. Rather I will refer to pins on the three plugs and how they need to be joined. I am not using any formal pin numbering convention here either; this is MY methodology.

All the plug types needed here may be supplied with various of the brass connector strips either fitted or missing. It's only important that those you NEED are present and in the right places. Unused pins don't need to actually be present in the plug - but in counting (numbering) the pins, include empty slots. I have used RJ45 as the basis for my numbering convention.

At the Fritz!Box end you need either a RJ45 or a RJ11 plug. The socket on the box will accept either. Placing the plug such that the brass pins are uppermost and the cable runs away,

my pin numbering convention for RJ45 is 12345678 (with 1 being the leftmost). If yours is a RJ11 (either will do) then that only has up to 6 connectors in it. I will number these 234567 to correspond with the equivalent positions on the RJ45.

DSL uses two cores. Analog phone uses two cores. Therefore, this purpose only uses pins 3456 (as highlighted); 4 & 5 for DSL; 3 & 6 for analog.
(Note that this description does not include provision for ISDN which does use 1278 and does need a RJ45).

At the other end, to fit a regular UK splitter or new faceplate you need both a RJ11 for DSL and a BT plug for analog phone.


RJ11 plug: 6 connector positions which I have numbered 234567 (only to conform to the dual purpose at the Fritz! end). 1 & 8 don't exist either as pins or empty positions. This purpose uses pins 4 and 5.
BT plug: 6 connector positions which I have numbered 234567 (for the same reason). 1 & 8 don't exist either as pins or empty positions. This purpose uses pins 3 and 6.

Despite some commentary online that polarity isn't important - as far as I could work out it does matter. By trial and error I found that this works perfectly:

Fritz! end (RJ45/11) pin 4 to RJ11 (DSL) pin 4 - and pin 5 to 5.
Fritz! end (RJ45/11) pin 3 to BT (analog) pin 3 - and 6 to 6.

If you can solder then I'd suggest the easiest way to go about making a cable is
1: Find or obtain cables with the required terminations: 1 x RJ45 or RJ11 with at least pins 3456 present and connected; 1 x RJ11 with at least pins 4 and 5 (the middle two) present and connected; 1 x BT with at least pins 3 and 6 (either side of the middle two) present and connected.
2: Cut the cables to required length and strip the cut ends to reveal the cores. Typical cable is thin and fiddly to work with and easily fractured. So do it with care.
3: Use a continuity tester to establish which colour core corresponds with the required pins on the attached plug. Make clear notes.
4: Cut back any unused cores out of the way.
5: Solder the joins, insulate them (shrinkwrap or tape) and then test overall continuity (and for shorts).
6: Job done.

I hope any Fritz!Box users find this useful.
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