Technically very good and reliable device not to be compared with DIY goods. 10 year lithium battery. Pollution compensation, ie automatic compensation at polluted smoke chamber. Self-monitoring through automatic self-test with error display. Silent standby, ie. no noise / bedroom fit) Easy Press button, ie the button for testing or mute is easily accessible from the bottom. (Broomstick) I have mounted in various apartments 12 piece, and all have passed my tests immediately. Strong buy recommendation from me.
