Microphone Circuit between Microphone and Radio Receiver (TO 12/2010): Description
WARNING: This page is about a different car, the 2011 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
This circuit sends the voice signal from the inner rear view mirror assembly (amplifier microphone assembly) to the radio receiver assembly.
It also supplies power source from the radio receiver assembly to the inner rear view mirror assembly (amplifier microphone assembly).