interface handphone to at89c51/52

hello...........
i'm student last year now i'm doing my thesis. i need some help about how to connect my cell phone to microcontroller exactly interface handphone to microcontroller. please help me........
and if you know about schecmatic of interface please tell to me. thanks

take a look at this schematic, I used this to connect a mobile headset's speaker o/p to the controller.
adjust POT to get a nominal current value.

I used this configuration for DTMF reception. I dont know for what purpose you need it.