2 boxes of 4 enclosures are defective: they signal "low battery" during the self test pulse, even with a new battery. professional electronics I added a capacitor of 47 microfarads on the battery connector to buffer during the self test pulse. the problem is solved and this will use the 9V battery to a very low voltage (7 to 8 V) otherwise the alarm "low battery" will fire at the slightest drop in voltage of the battery, even on detectors that appear to work normally with the installation. this material is of poor design. Board seller: trace information to the manufacturer.
