I had a strange fire alarm in my old house....?

[gyoubou]

Ok, In my other house that I previously lived in, we had some fire alarms that didn't seem to work properly. Of course, every time something let out a bunch of smoke they went off and stopped when they were supposed to. But, other days, it would be a normal day, and no one would have cooked anything that day or night, but they go off anyway and stop whenever they want, because they don't have off buttons. We changed the batteries multiple times, but that didn't seem to help. So, my father removed the batteries from all the fire alarms so they would stop beeping randomly. This, of course, made it so whenever something caused a lot of smoke they wouldn't go off. But, like before, they went off whenever they chose. This happened for a little while longer, up to where we were going insane from the fire alarms. So my father went around the house one last time and unhooked all the wires that connected the alarms. This led them to stop for a little while, then we started hearing something. It sounded slightly familiar so we drew our attention to it, and alas, they were beeping, not as loud or long, it was more of light, short beeps. If you're familiar with music terms, it was more staccato than normal beeps from a fire alarm. This has bugged me as to why they did that. Was the wiring strange and we just didn't unplug it all the way? This has never happened in our new home or anywhere else we have visited, has this ever happened to you?