Patent ID: 7000123

Claim:
A control device, in a first peripheral apparatus, for controlling a first voltage applied to a first conductor wire of a universal serial bus (USB) in the first peripheral apparatus connected upstream to a second peripheral apparatus, the first peripheral apparatus comprising a supply voltage source for supplying the first voltage to the first conductor wire, and the first peripheral apparatus being connected to receive a second voltage on a second conductor wire of the USB, the control device comprising: a detection circuit connected to the second conductor wire of the USB for detecting the second voltage received therefrom; a memory connected to said detection circuit for storing a logic value corresponding to a presence or an absence of the second voltage; and a logic control circuit connected to said memory for operating the supply voltage source only if the stored logic value indicates that the second voltage is present, to protect the second peripheral apparatus from receiving the first voltage via the first conductor wire of the USB of the first peripheral apparatus when the second voltage is not present.