[Freeswitch-users] Can't understand documentation

On http://wiki.freeswitch.org/wiki/Misc._Dialplan_Tools_record_session, at the bottom of "Activating via DTMF", it states: The other party doesn't hear the DTMFs but maybe its comfort noisy is disappearing for a very short time. When that sip client *starts* a call the above dialplan forbids activating recording. Can someone explain what these two sentences mean? Thanks, Lars