Attaching an MIC to SIM300Z module

Hi
I am newbie and need some help from experts here. I have an sim300z module. I have got the power supply arranged for it. I need help in attaching an MIC to the M1CIP & M1CIN. I have read the datasheet but I dont know what is "difference circuit" and also if the RI pin goes low for longer (I assume when receiving a call) and I send ATA, will the caller be able to hear from the MIC attached to the SIM300z.
The above questions may sound too simple for few people here but I am going insane finding info from the web without any luck so PLEASE help if you can.

Here is the link for the sim300z module datasheet.
http://www.symmetron.ua/files/SIM300Z_HD_V1.01.pdf