Good question. Sounds like these are powered speakers, each has an integral amplifier hence the power and signal conductors. Not my first choice for a life safety system but it doesn't look like this is well thought out anyway.
I haven't found any UL listed emergency speakers like this (hmmm I wonder what they are using) only paging speakers so I can only go by those specs. Typically that would be 50ma @24vdc per speaker- and that sounds awfully low.
-Hal
[This message has been edited by hbiss (edited 05-20-2005).]
