... communication channels,frequency-hopping technology,super eror- correcting capability ,so the conversation is very stable8)Untrashort bulit-in antenna design ,fashionable ... -13790170551Addres: 7#ZhongshanRoad,HeTanGang,Beizha,Humen,Dongguan,Guangdong, China check out the high tech video door phone ,rock and roll set up