Slightly wrong. The difference between supervisory and trouble, is that supervisory is a kind of "alarm" condition. That means you hook something up to a zone, and tell this zone is supervisory. If there is a problem with a detector on the supervisory zone, you will get a trouble. It isn't limited to power, it can be all troubles. Think like this: If you get a open loop on a supervisory zone, it will react with a trouble. However, if a supervisory device trips, it will short the loop, giving a supervisory signal. So basically, if you wire a pressure switch to a fire alarm zone, and tell the system the zone is a supervisory, then you will get a supervisory alarm. Change that zone to a "fire" zone, and the same pressure switch will pull a real fire alarm. A trouble means theres something wrong, for example, if that pressure switch breaks and become open loop totally, then you will get a trouble signal instead. In burgular alarm terms, "supervisory" is same as configuring a zone in your burgular alarm as "Temperature alarm". This zone, if its trips, will cause a temperature alarm to be sent to dispatch centre, and they call you and say, for example if you named your zone "Fridge", they will say "hey your fridge has some problems so its not cold enough". However, if that zone is shorted or opened, ergo having the wrong resistors, it will still react with a "Tamper Alarm" and sound the alarm. (which is same as "Trouble" on a FACP).
