a. Certain regions with weak even blind signal, such as underground or semi-underground places of business, basements, parking lots etc.
b. Small-scale areas with signal not strong enough, such as conference rooms, offices, small supermarkets, shopping malls and some special public places like public security system and road safety management.
c. Large-scale places with weak signal, such as hotels, bars, cafes, dance halls, clubs, KTV rooms etc.
d. Elevator, subway, tunnels, lift wells in particular, not in the lift cables laid.
e. Private cars, luxury yards, homes and so on