Abstract: A controller is usable with a tractor that has a power supply and a trailer that has first and second auxiliary devices. The controller is configured to selectively enable and disable each of the auxiliary devices based on a predetermined set of device disabling conditions wherein: When any of the device disabling conditions occurs, then both auxiliary devices are disabled. When none of the device disabling conditions occurs then, when a first device-selecting condition occurs then the first auxiliary device is enabled and the second auxiliary device is disabled. And when a second device-selecting condition occurs then the second auxiliary device is enabled and the first auxiliary device is disabled.

Abstract: In accordance with the teachings described herein, systems and methods are provided for supplying power to a vehicle trailer. A connection device may be used to connect the vehicle trailer to a vehicle power line and to a control line from a vehicle electrical system. The trailer may include a main trailer electrical system and an auxiliary trailer electrical system. The main trailer electrical system requires power only when the vehicle trailer is in motion, and may be coupled to the connection device to receive power from the vehicle power line. A control unit may be coupled to the connection device, and may receive a control signal from the control line. The control unit may be used to switchably couple the auxiliary trailer electrical system to the vehicle power line based on the control signal.