G3X Mono Audio: The mono audio output provides audio alerts for connection to an unswitched input on an intercom or audio panel. In this case it is to the GTR200 intercom.
PFD Audio out:
PFD J4602 pin 1 to GTR200 J2001 pin 9 (Aux mono IN 2) PFD J4602 pin 18 to GTR200 J2001 pin 28 (Aux 2 LO)