24-Channel, 8.5 mA, Digital I/O Device—The USB-6501 is a portable, bus-powered USB digital I/O device, providing reliable data acquisition and control at a low price. The device provides overvoltage protection its digital I/O lines and a 32-bit counter. With plug-and-play USB connectivity, the USB-6501 is simple enough for home and academic applications, but robust and versatile enough for laboratory and industrial applications.