Expandable with doorbell Receivers/Transmitters Several receivers(up to 20) can be controlled from a single transmitter. Each receiver can be controlled individually from additional transmitters. Different transmitters can be set to different chime. Long Operating Distance With a reliable wireless range of 1,000 feet and strong signal penetration. Enjoy a reliable and hassle-free doorbell system at home, in factories, offices, classrooms, apartment blocks, villas, and other large areas. 32 Chime Tunes with 5 Volume Levels The chime receiver has 32 pleasing ringtones to choose, you can set a simple  tune to reminder you. 5 levels of adjustable volume from 0-120 dB, enough to be heard anywhere you are in home. LED Flash Indicator The LED indicator on the doorbell receiver flashes when the transmitter is pressed and a signal is received. This feature is also helpful for those with a severe hearing impairment. Durable Weatherproof Button The push button waterproof rating is IP55, to ensures the perfect usage in rainy days. Works between -4°F to 140°F. 3-Year Battery Life The transmitter uses a 230 mAh CR2032 lithium battery which has an ultra-long three-year lifespan, freeing you from the hassle of frequent battery purchases. Memory Function It remembers your previous set melody and volume level - even after a power outage.