Since I bought my 2850VN last year I've had an issue where the telephone that's connected to it gets no dialtone immediately after a reboot, the tone returns only after an inbound call has been made to the phone (either via one of my SIP lines or via PSTN).

The SIP lines are definitely registered & outbound calls cannot be made from the phone either until an inbound one has been recieved (ie it's not an issue simply about the router not "playing" the dialtone). The phone has been changed & I've tried various firmwares (now on 3.6.4) without any success.

Has anyone got any ideas what I could try next?

You say there's no dialtone but it IS registered (I assume from the WUI you can see that) but what happens if you
life the handset - can you dial; do you hear the tones. Do you hear anything (voice back or white noise?)

Definitely registered as it shows on the router & can take incoming calls. If I lift the handset there's no noise at all, no dtmf tones if I dial & they're not even being passed to the router silently as I've tested dialling a number & just waiting to see whether a connection is made. No voice back either; it's as if the telephone is not even connected to anything but everything is fine once that first incoming call has been recieved.

Well, I'd say try a different phone but you already did It's strange; I've never come
across it so can't offer any suggestions.

Does the router show you going offhook; i.e. in the VoIP status screen I think it
shows offhook etc.

Router phone status stays as idle

With my testing yesterday I've found another workaround however - by plugging the telephone into Phone 2 the problem seems to disappear. I'll test this for a few days whilst doing periodic reboots & also try to find a different splitter as the problem could lie there.