RS232 TTL converter converts RS232 signal (+/-12V) to TTL level 5V and back +5V 2ma needed for power supply Normally processors need this with from UART to PC Saeage Barracuda 7200 firware problem This adapter is need to fix the Seagate problem http://murobbs.plaza.fi/massamuistit/564353-seagate-barracuda-7200-11-levyissa-vakava-vika-korjauksia-olemassa-11.html