have placed 5 pcs of the house and not worry so far. Zero false positives, easy to assemble and I just hope this time the battery will last 10 years. The old equipment already 14 years old (children as time is running) Been but were then also test winner and was a recommendation of the fire which had just compared multiple devices. The units were equipped with a 9V battery and one of the 5 devices always bugged sometime at night - BEEP exchange my battery, and now find that the time was :-). From a cost point of a battery has about 2 years held (Longlife 3 / unit, it should be already), making for 10 years about 15 per device. Cost of the device then 35DM (German marks). In this respect, today's devices are much cheaper in total thanks to modern electronics. Whoever still thinks about saving money on batteries exchange can also equal to the "low cost" cheap buy appliances with 3 false alarms during the week and there is no alarm in case of fire. I once disassembled an old machine and I must say - jo after 10/11 years, it is time to replace. The lenses of the transmitter and receiver are aging simply "blind", it is not alone the only dirt. After I saw the inner workings of the old equipment, I do not see it a second thought, but swap the device equal to even have an advantage after 10 years. Who, incidentally, never thought about fire alarms (like me 14 years ago) --- In the neighboring village is then a house burned, a child died of smoke inhalation because no one noticed, there were no smoke detectors mounted ....... unfortunately ,
