Over the weekend, I had a look to see whether there was any new firmware available for our DSL/WLAN router and handset, and found some.
The change that interested me most was the introduction of a new "eco mode": if the router/base station knows that there's only one DECT handset coupled with it, and if it detects that the handset is resting in the base (perhaps by detecting the charging current?), the DECT transmitting power will be reduced to "almost nothing".
Which makes sense, since if it knows that the handset aerial is only a few centimetres away from its own, it needn't put out much power to communicate with it, whereas if it doesn't know where the handset is, it has to produce a stronger signal just in case it's a bit further away.
Something pretty simple in retrospect, but something I probably wouldn't have thought of.
(After installing the new firmware, I can't access a couple of submenus in the handset anymore. I just got an answer to a support request I opened because of that and they told me to turn the handset off and on again; will have to try that when I get home this evening. If that doesn't help, they advise to reset the thing.)