A direct current electric system includes a DC link, a first energy storage system, a second ESS, a coupling device, and a bidirectional DC-DC power converter. The device includes a key input unit including at least one specific key for terminating reproduced music; and a controller for controlling termination of the reproduced music when an input of the specific key is maintained for at least a predetermined amount of time. The engine also includes at least one camshaft positioned in the head and a cam retainer positioned over the camshaft to retain the camshaft in the head. The radiologist then runs a program on the computer that compares, bit-by-bit, the two digital images and identifies and highlights all differences between the two. The CEC controller also waits for the wireless interface transceiver circuit to receive a wireless ACK packet for the transmitted wireless data packet. The insulating housing defines a card insertionejection direction.