I have a fire alarm that accepts a 25v line level speaker input at 4w, what is going to be the easiest way to play arbitrary signals over it i.e. from a 3.5mm jack, an amplifier and a transformer? are there small pre built modules for this purpose? Everything I see seems like it is intended for distribution to a large pa system not a signal speaker.
Edit: It is a SSPK24-75WR Here are some datasheets I could find, but there is not mutch info beayond "hook it up to our system" http://resource.boschsecurity.us/documents/Datasheet_SSPK_Famil_Data_sheet_enUS_2736837259.pdf