When your smoke detector makes a repeated beeping noise, it is usually trying to signal that the batteries within the unit need replacement. Once you have placed new batteries in the unit and reconnected it to the base, the beeping should stop. However, the noise can also signal you that something else is going on. Some smoke detectors will continue to beep if the batteries are replaced but the unit wasn't properly put back together. Check the battery door on the unit to make sure it was re-inserted properly and sits flush with the rest of the unit. If you have checked to ensure the batteries inside the unit still work, and the unit is properly put together, there may be an issue with the unit itself or the way the unit is connected to the fire detection system. To be safe, the best thing to do is have an expert take a look if you can't determine why the smoke detector is continuing to beep. The smoke detector may need to be repaired or replaced.