Hello sir/madam, My name is srinivas.for my microcontroller interfaing to GSM modem application, first i tested GSM modem with PC that time , i am getting a new problem while interfaing PC with GSM modem.when i am interfacing PC to GSM modem with total 9 pin DB9 connector RS232 cable, it working fine. But when i am interfaing GSM modem to PC with(Rx,Tx and GND) 3 pins , its not working. how i overcome this problem . please help me, bcoz for application i will provide those three pins only.i.e,when i will GSM interface to microcontroller , i will provide those three pins only. please help me and if you give through suggestions this mail also oltc@inteluxindia.com. Thank you very much.