Sony ericsson phones follow the omtp standard along with other manufacturers, while other follows the ctia standard. The difference of these two standards is the wiring to the 3.5mm plug. Therefore if you connect a ctia headset to a sony ericsson phone, you might get reduced functionality or it might not work at all (depending on accessory and phone model). If your headset is listed as "compatible with iphone" it follows the ctia standard. If you have a headset that follows the ctia standard that you would like to use with your sony ericsson phone, this adapter 1249-0456 ec250 converts it to omtp.