Does anyone know what the telephone module really does?

 

It should be identical to the one in my CTT. Basically, two things. One, it has a SIM slot that you can put into and it uses the aerial antenna to get signal. Basically turns the car into a QuadBand GSM phone. Second thing it does, if using a phone with rSIM access (i.e. Android and some jailbroken models of iPhone), it slaves the SIM card of your mobile over a bluetooth connection and allows you to use the roof/trunk mounted antenna. Again, more signal ability. Either way, allows you to read/reply/compose texts on the screen as well.

Hope it helps. Love mine...

J