Which type of microphone to use with Motorola M930?

Hi
I've installed in my car a fixed Motorola M930. the microphone that I've used is the microphone that was connected to my old handsfree kit. I believe that its the wrong type because the person that I'm calling doesn't hear me (the other way around is ok). could you tell me if indeed it's another type of microphone and if so, what sort?
thanx.