... ,high fidelity,stereo speaker,cordless receiver,digital signal,education 2.4G Digital Wireless On-Wall/portable Speaker can be ... selectable channels, simply to avoid interference: the item works in 2.4GHz ISM (namely Industry, Science, Medicine) band, with 20 channels ... be widely used in education, medicine, advertisement, speaker, family, security, office, meeting and so on, is a best choice to ...