The TR1 series transformer relay adapter is a pre-assembled autopilot interface unit that follows the interconnect specifications and component requirements recommended by the manufacturers of certain PFD systems when interfaced with existing autopilots. Rather than designing their own assembly from several components, installers can install the TR1 which is already housed in a small aluminum enclosure with the same wiring interface outlined in PFD installation manuals.This TR1 series transformer relay adapter (EDMO# TR1R) is for Aspen Avionics primary flight display installations when interfaced with Century autopilot models 21, 31, 41, 2000, and 4000 with flight director. *Must specify 14 or 28 volt when ordering!