Phonic America has released a new universal wireless system designed for speakers. The WMSYS-3 is a mono system And the WMSYS-4 is a stereo system The receivers are slightly larger than a pack of playing cards and both transmitters and receivers come with power supplies. No batteries required. We've used the systems several times and not experienced any problems even when transmitting through walls. Each system features 16 selectable UHF frequencies.