For My Kevo Contemporary, Why Doesn't A TTO Work When Someone Is Standing Behind The Interior Of The Door?

Kevo Contemporary has an IR (Infrared) on the interior so if someone is standing right behind the door, a TTO will not work. The intent is to add support to inside/outside technology detection, so if someone is inside the house, and right behind the door, IR will detect ion when someone is on the inside, in case inside/outside algorithm doesn't.