"The best business telephones in the world."

Hi,

I'm using a Snom A100M (100M4341004242) connected to a Snom 870 (old, I know).  If I put the headset volume to more than 66% the person at the other end reports that they can hear themselves.  I tried setting the headset mic volume  down to 1 in the web interface (8.7.5.35) but it makes no difference.

I tried plugging in the headset on the handset port and the handset on the headset port in case the problem was with the port on the phone but the problem moved with the headset.  Is there any setting I can change to solve this problem?

If I use the same headset on a Snom 215SC (with the Snom 2.5 jack) the problem doesn't seem to happen, so it could be a cable problem on the RJ11 cable, but is unlikely that it would only happen at certain volume level or maybe the 215SC maximum volume is lower than the 870 66%.

I thought of buying a Snom A170 but the 870 is not listed as compatible with the A170.  Is that because it's old and you removed it from the list or because it actually doesn't work?

Thanks and regards,

Federico