On my Snom 300 I can hear myself when I talk on the phone - it's a really annoying echo.
Is there a setting that I can turn off somewhere? When I got to put the phone down you can head a loud pitch squelch (like when you put a mic next to a speaker)!
For anyone who's interested, I adjusted the following setting: Advanced - Audio (Tab) - Audio (Section): Headset Mic Volume from a '7' to a '6' and now I have no more echo on calls. :)