SKU # 866606000 PART # 866-606-000   RD-C1-D3-B-E3

Janome Needle Plate Sensor Switch Unit 

This is the code reader to detect the different needle plates on the machine.  If you have a machine with pop-off plates, where, when you clip a plate on, the machine detects whether it's a zig-zag or straight stitch plate, and your machine isn't detecting one plate or the other, this is most likely the part that needs to be replaced. 

For Janome:MC 6650P, MC 6700P

For Elna 720, and Elnita EF72