Powered USB
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Powered USB uses standard USB signaling with the addition of extra power lines. It uses four additional pins to supply up to 6 A at either 5 V, 12 V, or 24 V (depending on keying) to peripheral devices. The wires and contacts on the USB portion have been upgraded to support higher current on the 5 V line, as well. This is commonly used in retail systems and provides enough power to operate stationary barcode scanners, printers, PIN pads, signature capture devices, etc. This modification of the USB interface is proprietary and was developed by IBM, NCR, and FCI/Berg. It is essentially two connectors stacked such that the bottom connector accepts a standard USB plug and the top connector takes a power connector.
Read more about this topic: Universal Serial Bus, Power