sir my project is to automatically send an sms through gsm modem to the doctors mobile using a microcontroller whenever the threshold limits of blood pressure,temperature,heart beat etc are crossed so please suggest which microcntroller to be used and the mobile to be used and the necessary circiut with source code
ok sir i understood db9 connector but should we insert any capacitors or necessary elements between microcontroller 89S52 and rs232 pls provide me the circuit related to this and the link which u sent is not working.can u suggest other link if any.
I don't have circuit diagram. For MAX232 you will have to connect some capacitors. Details given in the datasheet.
Other than that you don't need any capacitor or any other element.