IMHO, the best solution on the Flex is to either:
- Switch OP 3 to switched DC, set as output PA (this output will fire on silent or audible PA), then place a wire link from OP3 to an input zone set as PA with resistance set to NC. You cannot have a speaker connected if selecting switched DC.
- Add a RIO, leave OP3 as speaker. Set a RIO output as PA, place a wire link to an input zone set as PA with resistance set to NC.
Implementing this way, the panel will trigger a full blown audible PA with external siren and strobe which requires code entry to silence.
For those with a VMOD, you can simply program HA/NodeRed to loopback from the PA output to a virtual zone without any physical link.