Matching microphone in a phone

I am trying to interface a handsfree headset to a desktop speaker phone. I am trying to use the speakerphone speaker and microphone leads to connect to the handsfree set so I can leave the phone's handset in the cradle. The microphone in the phone base has only two wires to it. I connected these to the handsfree mic leads but it doesn't pick up the sound. Is this just a impedance mismatch or are the two mics (phone and handsfree) just not the same type? How do I tell what type they are and/or test them? Any suggestions on how I can make this work?

By the way, I am trying to interface a Nokia headset that has 4 seperate contacts in the plug. I assume they are positive and ground seperately for both the mic and speaker. Does polarity of the mic matter?

Polarity of the mic should not matter. How do you know which two wires are the mic and speaker? If the mic is magnetic, you will need a preamplifier. If the resistance of the mic is low, it is most likley magnetic. If the mic measures open circuit, it is probably electret and should work if the amplifier in the speaker phone is high impedance.

I'm assuming that since there are 4 wirres in the plug, 2 are for speaker and 2 for mic. This is the standard earbud type handsfree that has the dangling mic. I'm using this handsfree because the speaker and mic in the speaker phone also do not share a common ground. Are the mic in the common handsfree for a cell phone usually a certain type? (electret or magnetic) How can I tell if the amplifier in the speaker phone is high impedance?

Measure the resistance of the mic in the speaker phone. If it is different than the resistance of the mic in the headset, you will need a preamplifier. You don't need to disconnect the mic to measure it.

I don't get any reading (resistance) on either mic. Both in the speaker phone and the handsfree they read as open circuits.

if its an electret mic, it wil matter the way that you connect it. Take a ohmeter and put one lead on each leg leg, and the other on the mic case. One of the legs to the case will measure as being connected. The other will measure as an open circuit. The leg that is connected to the mic case is the one that should be connected to negative.

If both measure as an open circuit, tehn its probly not an electret.