All of the Batfish klaxons are missing. So, I can't verify if the horns were 20VDC or 120VAC. However, I do know that the input power into the 1MC/7MC stack is 120VAC. More than likely, the voltages are rectified and stepped down for the horns, just like they are for the speakers. Most electronics run on DC voltage. AC voltage is good for power transmission, but it's necessary to convert to DC to run your home computer and TV, for example.