Current is supplied from the B/U LP fuse to the back up lamp switch through CKT 839. When the switch closes, voltage is applied to the VEH B/U and TRLR via CKT 24. Voltage to the lamps is supplied on CKT 1324. CKT 1324 also supplies voltage to the HD trailer wiring connector and the electrocromatic mirror. For the LD trailer wiring, voltage is supplied from the VEH B/U fuse. CKT 1324 supplies voltage to electrocromatic mirrors. CKT 1624 supplies voltage to H.D. Trailer wiring connector.