Only one horn/strobe, and it was just beeping

[peter d]

I don,t know about all horn/strobe devices but the ones I have installed have three terminals, one negative and two positives. If you put the negative on one of the positives and one of the positives on the negative how does this not affect the whole loop.

In that case it would. But in a regular 2-terminal device where you wire it backwards it would have no bearing on the loop at all.