2 transmitters, 1 receiver 【IP44 Waterproofing】: The transmitter is splash-proof (equivalent to IP44 waterproof standard), with excellent waterproof and dustproof performance, allowing use outdoors or in the bathroom, without worry on rainy days. However, avoid submerging it in water or using it in places where it is directly exposed to rain. 【Stable Transmission】: This calling chime transmits wirelessly up to 300 meters (manufacturer's specification) in an unobstructed area. The highly sensitive receiver can stably receive signals through walls, wooden doors, steel doors, etc., and can be used in two-story buildings. Installation is easy without any construction. 【Volume Adjustment & 36 Selectable Melodies】: The loud calling sound can be adjusted in 4 levels, with a volume range of 0dB to 100dB. 36 melodies are selectable, satisfying a variety of environments and needs. Recommended for those with hearing difficulties due to the loud volume. 【Easy Installation】: This doorbell chime requires no wiring. The doorbell receiver is battery-powered, and you can fix the transmitter to the door frame (adhesive tape is possible) and the chime will play when the button is pressed. Installation is very easy as it can be done without any construction. Children and the elderly can also use it. 【Wide Range of Applications】: Can be used for home security, restaurants, offices, hotels, and nursing care settings. Usable in various environments. In addition, it is useful for calling at the entrance, reception, meal times, and for visitors, and also helpful for those who need assistance in izakayas, adapting to various scene needs.