Coupler for handset cords.
Hard to find, but we have 'em.
Product Description
Sometimes you need a cord that's longer than normal. Or maybe you need to lengthen a cord but you can't unplug the present cord from the phone.
If you're in either of these situations, this special coupler will help you out. It works with standard 4-position/4-conductor plugs used on most handset cords.