Zen fritzbox 7530AX and BT4600 DECT handsets

Should the DECT base functionality on the FB 7530AX work with BT 4600 handsets?

I got hold of some 4600 handsets from a relative and as I have Zen Fibre and the Voice functionality I thought I would ditch my old DECT system (which connected via its own base to the FON socket) to try out the features of the 7530.

However despite the fact that the handsets will register with the 7530 if I try to make a call on any of them they just show "Line in use".

I can see the handset details in the 7530 admin DECT screens so they seem to have registered.
If I call the house from my mobile they don't ring.
The old system is unplugged and no other extensions in the house.

I spoke to Zen and they said I need a VOIP phone and that the 4600's wont work but this sounds absurd (their evidence for this was a link to a random sales page).

The Fritzbox supports DECT-GAP and the phones do as well (as far as I can tell) and the fact they register seems to indicate there is hope but I don't know what else to try.

Any ideas?
Anyone got a DECT handset working with the 7530AX?
Are their different flavours of DECT?
Is VOIP a different thing to DECT?

DECT is different from VoIP and DECT is not dependent on whether the underlying line is PSTN or VoIP as that is more a property of the line setup on the base unit.

I have a DECT single handset setup on the Zen Fritz!box 7530 (non-AX) router.
When I enabled the DECT base unit function on the router it prompted to register the first handset.

On the handset out of the box (after charging) I used the menus on the handset to initiate registration.
I didn't do anything else with the analogue base unit other than use it as the charging base.
I didn't need to de-register the handset first
(I believe some handsets have this function or otherwise use the docking action to complete initial registration to supplied base?).

The handset by default was expecting a base unit pin of 0000, which worked automatically.
If I deleted the handset from the Fritz!box and altered the base unit pin on the Fritz!box UI then re-registered the handset, it prompted for pin during registration.

The handset is working for calls and is automatically used for the external phone number as well as having its own extension number (*6xx)
and also the Fritz!box security functions where it asks you to confirm certain changes or a reboot by pressing a button or keying a code on a connected phone (proof of in-person change).

I've added a few phone numbers to the Fritz!box default telephone book which is supposed to provide to the handset but have not figured that part out yet.

Handset model: Panasonic KX-TGB610
Pretty basic model but in retrospect I would have chosen one with backlit keys (screen is ok).

Also I guess you can obtain the handsets separately or with a charging-only base (where sold as add-on units rather than as starter set).

Thanks for the reply prizx.

So as I thought the 7530AX can work with DECT handsets and the Zen support guy was completely wrong in what he was suggesting.

Last night I thought that I would try one of the old handsets (BT Diverse 4016) I was replacing and see if that would work with the 7530AX,

Despite being at least 15 years old and also a BT system it worked! It was able to pair with the Fritzbox without problems and make and receive calls.

So it would seem that....

a. The 7530AX can undoubtedly work as a DECT base station (despite Zen support saying otherwise).
b. The BT 4600 handsets don't work work with it (at least not in my case).
c. Handsets from a BT Diverse 4016 WILL work with it.

Cheers

Andy

From the AVM website:

‘The cordless telephone must support the DECT-GAP profile.’

Not all DECT phones meet this requirement.

Needs IQ 2 or higher to work with Fritz box/DECT. I use Gigaset A690HX. Bit basic (eg backlight not adjustable) but works. If you want to use with old hardware then need to use an analogue connection from FON connector to your base station. Don’t forget as well as setting up the connection to voip server you need to add the telephone as a device before outgoing calls will work. I also have Fritz telephone app on me mobile and iPad so I can live the true couch potato life.

In reply to a post by GoWest:

‘The cordless telephone must support the DECT-GAP profile.’

That's the key to DECT - GAP compliance. Some even claim to support it but they either only support a subset, or support it in such a broken fashion that it is indistinguishable from not not supporting it.

Carrier-branded handsets are probably the worst for it - even though they're standard glue'n'go shovelware designs like their peers - Carriers are prone to "improving" things in firmware.

I suspect the support person was hedging on a couple of points, that it is possible the BT branded hardware may have been sold bundled with and locked to a specific service (similar to what happens with some mesh Wi-Fi pack sold on subscription) and that due to age of tech may not be completely interoperable, (GAP and IQ version as mentioned in other posts).

However a better choice of words would be for support to say that there is no guarantee that 3rd party items are fully interoperable as they can't account for all permutations or lock-ins, but you can try anyway and see (as you have done).

I should add as I have nothing plugged in the FON port I have set that as do not disturb 24/7 so that it is never attempted for incoming calls.

I didn't have a spare RJ11 cable anyway to to connect the old phone with the FON port (which is not a socket for the BS 6312 431A plug with the side-clip).