Pinout by Cruiser team:
CTMS stands for Control To Mobile Station; CFMS stands for Control From Mobile Station; DTMS stands for Data To Mobile Station; DFMS stands for Data From Mobile Station
Standard cable is Sony Ericsson DCU-11
The (Tx)&(Rx) are reverse for K300i model, you must connect CTS & DGND together on board and connect the common wire to CTS(Pin3) in phone connector. If your cable is working fine then dont change it.