To criticize is only that an important indicator of the seller lacks! "Attention when using batteries!" Namely that work with 1.2 volts instead of the usual and for the device matching 1.5 volt alkaline batteries! The 1.2 volt batteries cause many buyers already mentioned "constant glow" red diode! On request from the seller I was told that the voltage of 1.2 volts is too low for the device and is signaled by a permanently lit, that the "batteries" should be changed. The functionality is however apparently not affected. Long-term testing will show's ....
Otherwise, there is nothing to complain about. Sellers provided a great service when requesting information and even sent me a replacement unit when I mentioned the problem with the red diode to exclude any malfunctions!
