1)  Suitable for homes, office and other place to install. 2)    32 melodies music for option. 3)    Transmitter uses 1x12V 23A battery (supplied) 4)    100m operating range(in open area) 5)     Easy to install 6)     No electrical wires to install 7)     Suitable for Hard of Hearing with Strobe feature 8)     Low power consumption 9)     CE and ROHS certificate *Although line of site is not required, the maximum range is based on optimal conditions with minimal interference. Wireless range is affected by objects such as walls, trees, etc. Actual range may vary, depending on environment. Model No. 601 Frequency 315MHz±0.5MHz 433MHz±0.5MHz Active pressure wave(receiver) ≤-57dbm Negative pressure wave(button) ≤-36dbm Power supply(receiver) 2×1.5V AAA Power supply(button) 1*12V 23A Alkaline battery Working power consumption ≤5W Transmit power <10mW Operating range UP to 100 meters(OPEN AREA) Sound options 32 melodies option