BRK 770MRL Ionisation Smoke Alarm, Mains Powered with Rechargeable Battery Backup, Push Fit Base

The alarm itself is probably fine. I haven't had it installed for long enough to know. I had a couple of issues fitting it: 1) The MRL requires you to replace your base / connecting plug if it is of an older sort that works fine with MBX or MC (now obsolete) alarms - so beware of this if you are fitting to an exiting alarm system. Nowhere in the fitting instructions does it mention this. It plugs in fine and looks like it is working except that it goes 'feep' every 45 secs indicating low charge on the battery - this never stops. The newer base connects two previously unused pins that enable the battery (and in retrospect is obviously required to stop it going 'feep' all the way from the factory). This took an number of confused (on my part) emails with the seller to sort out. My primary complaint here is the lack of documentation stating this. 2) The push fit "choc block" connectors for the wiring work very well if you only want to push in one wire, but if you need to connect two (as you will for many multi-alarm systems) then one of them always wants to fall out.