loop isolator mainly used to isolate a portion of a short circuit on the bus, other devices on the bus to ensure normal operation. Upon elimination of the short circuit fault, loop isolator can be isolated out their own part back into the system. It is worth noting: AW-D314 loop isolator  using the bus to facilitate the determination of the location of a short circuit.
 
Addressable Fire Alarm System Loop Isolator Module Feature
In the event of a short circuit isolates faulty parts of the loop
Automatically resetting once the fault has cleared
LED lights indicate status