Some devices, such as high-speed external disk drives, require more than 500 mA of current and therefore may have power issues if powered from just one USB 2.0 port: erratic function, failure to function, or overloading/damaging the port. Such devices may come with an external power source or a Y-shaped cable that has two USB connectors (one for power and data, the other for power only) to plug into a computer. With such a cable, a device can draw power from two USB ports simultaneously. However, USB compliance specification states that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered."
Some devices , such as high - speed external disk drives , require more than 500 mA of current and therefore may have power issues if powered from just one USB 2.0 port : erratic function , failure to function , or overloading / damaging the port . Such devices may come with an external power source or a Y - shaped cable that has two USB connectors ( one for power and data , the other for power only ) to plug into a computer . With such a cable , a device can draw power from two USB ports simultaneously . However , USB compliance specification states that " use of a ' Y ' cable ( a cable with two A - plugs ) is prohibited on any USB peripheral " , meaning that " if a USB peripheral requires more power than allowed by the USB specification to which it is designed , then it must be self - powered . "
What does USB compliance specification prohibit?
What does USB compliance specification prohibit ?
"use of a 'Y' cable (a cable with two A-plugs)
"use of a 'Y' cable (a cable with two A-plugs)