The mic is simulated to be a sinusoidal voltage from 0V to 5V (DC 2.5V, amplitude 2.5V) passing through a voltage controlled 10mV/V, then a NPN transistor collector biased amplifies that signal. The analog output is at the collector. 5V simulate it's an Arduino "energizing" the "mic" and receives the signal to A0 from transistor collector.
