Wireless Doorbell, 2 Transmitters and 1 Plug-in Receiver No Battery Required for Receiver 58 Ringtones | CoolqiyaLong Distance Transmission Operates at a highest distance up to 1300ft in open air. Strong Working Signal doorbell for most material door or wall, including glass, metal, wood Wireless Multiple Doorbell You can expand 20+ door bells (receivers) & remote door buttons (transmitters). 58 Ringtones and Four levels Volume to Adjust; The door bell will keep the setting when power is removed. IP55 Waterproof & Easy to Install 1. Wireless no batteries