IRS2092 questions with reference design IRAUDAMP7D

I have a question when I am Looking at Amplifier Schematic, Channel 1&2 and the FET2 that cause of RED LED lighting.
The FET2 control by SD through a diode and resistor connected to a gate pin of the FET.
I understand the SD signal coming from the protection circuits is a value of a negative voltage.
My question is how does this voltage cause the FET to switch so that the RED LED
(Prot) turn on?
Is there a connection to the fact that the same SD signal is also connected through the diode and the resistor to the CD pin of IRS2092?

Thank you
Doron