The DC515NBS mutes the doorbell for 2 minutes so you can relax free from disturbance. The innovative halo light will also alert to the presence of a visitor when the doorbell cannot be heard. The doorbell comes pre-linked and ready to install straight out of the box, with optional screw-free installation and an easy open battery compartment so you can be set up in minutes.- Up to 150m wireless range- Digitally enhanced sound- 84dB maximum volume (can be heard up to 80m)- 6 melodies (hello, ding dong, westminister, marimba, telephone and soft alert)- No wiring required- Fixings included- Secret Knock function allows a different melody for friends and family- 7 colour halo light & LED strobe for visual alerts- Volume control- Sleep/mute mode