Expandable wireless doorbell set, 1 receiver (plug-in for socket) and 1 transmitter. The wireless doorbell set can be expanded with several receivers (max. 50) and transmitters (max. 50).Long range of 300 meters Sufficient radio range between receiver and transmitter. E.g. the receiver on the 2nd floor works smoothly. Your visitors will never miss you.5 volume levels and 58 ring tones different melodies are available, e.g. chord, jazz, folk music and so on. Volume is adjustable from 0dB to 110dB. You can set different ring tones for each receiver for each transmitter. When the bell button is pressed, the receiver and transmitter display a blue LED light. The hearing-impaired will not miss visitors.LIFETIME CUSTOMER SERVICE: We offer a 24 month warranty and lifetime technical support. All defective parts just need to contact us for a free replacement. 24 hour customer service to achieve your 100% satisfaction.