A digital receiver unit (28) having a backup energy source (214) for use in a vehicle (250) that operates on a primary energy source (216) includes a receiver (203) powered by the primary energy source when the vehicle is operating, a switching mechanism (210 and 212) for switching the receiver between the primary energy source and the backup energy source and a controller (210) coupled to the receiver for controlling the switching mechanism. The receiver receives data during a scheduled predetermined time and the backup energy source powers the receiver during the scheduled predetermined time if the vehicle is not operating.