787 cargo fire detection system
 

Not sure if we have any specialists on pprune able to answer these questions.

I understand the 789 has 28 photo-optic area smoke and fire detectors for the cargo hold. I assume these are purely smoke (rather than temperature) sensors.

Are the forward and aft cargo hold temperature sensors (as displayed on the synoptic) different units......is there a single sensor for each hold or are they multiple like the fire detectors?

The smoke detectors will sense both smoke and temperature.

The fwd and aft holds also have zone temperature sensors.

Not sure which sensors or combination of sensors give you the indication on the air synoptic display.