BOB,
You should be able to put horn strobes in, however they will probably not sync. Depending upon the number of horn/strobes your adding you may want to add a firelite power supply. From ADI the 6 amp 4 ckt one in this area is about $450. In most cases if more than one signal device is within sight of another they will need to be synced, however if its only one strobe per bathroom, and One horn/strobe in the main area, you could fly with not having them synced. Another option is a sync module I'm not 100% sure on this but the wheelock one is very straight forward.If you run a 2 wire class A loop for your devices start @ the sync,and return to the sync. You can tap out of the Nac ckt. at the panel, assuming you're not adding too many devices. The only catch is the wheelock sync will only sync wheelock devices. But most brands have they're own sync mods available. Some are just more complex than others.
