... wireless voice doorbell with clear voice for hot sell 1V21,2.4G ISM Public Frequency Band:2402MHz-2479MHz2,Transfer rate: ... than -100.Product Name: Wireless Voice/Non-visual Doorbell 1,2.4G ISM Public Frequency Band:2402MHz-2479MHz2,Transfer rate:250K ... be uesd in offices,workshops,homes,buildings ect.Using the 2.4G Communications Channel, full-duplex interoperability intercom, communication distance ...