high speed usb client 200 stops operating the data lines d and d u2212 transitioned into the se 0 state all with low levels s 5 in the se 0 state the usb host 100 detects disconnection with the bus powered high speed usb client 200 s 6 and an internal state of the usb host 100 is initialized s 7 the usb host 100 turns the switch sw 1 on s 8 to supply the power voltage to the bus powered high speed usb client 200 the switch sw 1 being connected to the power line vbus by the switch sw 1 being turned on the bus powered high speed usb client 200 is rebooted by the power supply and the positive data line d is transitioned up to the high level s 9 when one of the data lines d and d u2212 has the high level for the predetermined time t 3 the usb host 100 detects a state of connection with the bus powered high speed usb client 200 s 10 and resumes data communication with the bus powered high speed usb client 200 s 11 fig1 through 3 illustrate the bus powered high speed usb client 200 having the pull up resistor r 3 connected to the positive data line d in which according to presence of the power.