Yesterday I swapped out a bunch of M7310 sets for T7316e sets. One of them had a little amplifier (Walker) like you would see on a headset. I plugged it into the handset port on the set like the old one and it sounded ok to me but the user called today saying the volume was too low even when cranked up to max volume. I had him move the plug from the handset port to headset port but he said it made no difference. Has anyone heard of issues with T series sets and handset amplifiers?