Ian I would think that in the case of airliners they have so many redundant systems that if one goes down they have two or three others to continue with, so there is no emergency situation in there case. Georges -------------------------------------------------------------------------   You do not have to have more than one level of redundancy to basically eliminate any chance of total failure of the system with failures in the 1000 hour range such as fuses as long as the pilot has time to try the backup system? I will take reduncancy ever day of the week compared to a single CB circuit albeit it I have parallel master switch circuit breaker's but I do not intend to reset one as long as the other is working :>)   I know we are not changing anyone's veiws on CB vs fuses, but it has been an interesting dialogue.   Bernie