Wireless doorbell With 1 plug in receivers and 1 push button transmitter 36 Melodies & 4-Level Volume & Silent Mode perfect for classroom, homes or apartments Easy install Plug and play. can pair more transmitter and receiver to meet your need. 36 Melodies & 4-Level Volume & Silent Mode ringtones such as classic "ding dongs", pleasant melodies and more. 4-level of volume range from 25 db to 80 db Ultra-low power consumption design, sustainable use of Energy. Functional between -30 °C to 70 °C, FCC, CE, ROSH certified.