Fix faulty AICO/IE smoke alarm which is constantly beeping

Hi, I have an Aico/Ei mains-interconnected smoke alarm in my kitchen which is making one loud beep every 30 seconds. The green light stays permanently on, and the other alarm in the hallway is not beeping. I'd like someone to come out, identify the fault and repair or replace the faulty detector, while ensuring the interconnected alarms remain working.