This is from a code I pulled from another form (http://forum.arduino.cc/index.php?PHPSESSID=f32jdftivuehdidac12j50uk93&topic=49133.0 it's the last code posted on the first page of the forum) and I need to annotate it and be able to explain what every thing does but this last part is really throwing me for a loop. Any help you can give would be greatly appreciated XD

```
ISR(TIMER1_OVF_vect)
{
overflows += 1;
}
ISR(ANALOG_COMP_vect) // interrupt service routine that wraps a user defined function supplied by attachInterrupt
{
tnow = TCNT1; // current time
edges += 1;
if (edges == 1) { // Start counting edges.
tstart = overflows*65536 + tnow;
}
else if (edges == cycles + 1) { // Stop counting edges.
tstop = overflows*65536 + tnow;
// Turn off Timer/Counter 1 and the comparator.
ACSR = 0; //Analog Comparator Control and Status Register set to zero
TCCR1B = 0;
}
}
```