A small, attractive unit that immediately alerts you when your baby starts crying. Adjustable sensitivity control, can be set to alert you to sounds as soft as a baby's whisper. Plugs into any outlet in the baby's room. So your baby is not disturbed, no lamp flashes in the baby's room. When your baby cries, the BC 400 sends a signal over your home's electrical system to remote receivers, so it is completely wireless!. Built-in indicator light to show you it's working.