The 712 T is a Janome 712 without a motor. It has a special hand wheel for use with a treadle belt. The adds I've seen state that the machine can not be motorized. I've seen a motorized 712 and the motor is internal, so I suspect the motor parts are just not there. What ever else is different I don't know.
{
http://content.janome.com/index.cfm/...Specialty/712T }
Joe