I have an issue with a fire alarm system. When the fire alarm goes off, all the callpoints come back with no reply which are scattered throughout the loop. After the alarm has been reset and system has been reset everything returns to normal.  The system uses bases Sounders. I have checked for circuit overload and everything is in limits. I have checked the callpoint to make sure they are not isolators, which they are not. Any ideas what can cause this?

You would be better off asking the fire alarm engineers who have their own dedicated forum.