The Rx and Tx pins are inverted for use configuration swiches Nortel network types. It is better to buy the next product that I also successfully tested: ; Ie = UTF8 & qid = 1391609048 & sr = 1-1 & keywords = UC232A It will provide an extension COM socket / socket to plug one side of the male adapter COM port and connect the other side of the extension male COM port of the switch. Here is the link to the pin outs of a COM port (do not confuse the front and rear views of the RS232 COM port =): [...]