... well as parallel and USB ports on some models. Compatible with most Windows operating systems. No IRQ, I/O address, DMA ... requirements. Serial port models require no external power. Models with USB output ports use an included power supply.Features1.Plug and play ... USB1.1 or 2.0, EIA RS232 standardUSB signal VCC, DATA+, DATA-, GND, FGRS-232 signalRX, TX, RTS, CTS, DTR, DSR, DCD ...