Wire free: No wireless in-wall installation , wireless doorbell is battery operated (Maxcell CR2032)for fast and easy use. Lifetime lasts 300,000 times.The portable wireless plug-in receiver plugs into any standard outlet. Ringtone:Provide 48 different options of ringtons , 4 volumes for adjustment, allow your wireless door and window entry alert system to meet any need. Built-in Led Indicator: With the built-in LED indicator, the wireless door alert receiver and sensor offer additional assistance when coupled with the receiver to the hearing impaired. Difficulty hearing is no problem with our wireless doorbell. Free style combo: Each receiver can be paired with up to 32 transmitters like magnetic sensor ,PIR motion sensor etc.Each transmitter can be paired with mutil-receivers. Easy install: With its simple wireless plug-in and double-sided tape, the wireless door and window chime sets up in seconds. All hardware is included, and ready to use.