wireless door bell 1 Clear voice and stable siginal 2 >500m communication distance 3 Duplex handsfree call 4 CE/ROHS approve wireless door bellElectical Characteristics1. Using of 2.4G ISM public band :2402-2483MHz.2. Air transfer rate is 250K3. Transmit Power:20dBm or less(100mv or less),Receive Sensitivity;-100 or less.4. AFH Adaptive Frequency Hopping Technogy,Super anti-jamming capability, ...