Byron VD71 Elegant door video intercom with slim-line metal outdoor unit. It is fitted via a surface mounting bracket. It features a lighted push button with name plate and has an adjustable bell volume. Its cable extends to a maximum of 30m. It also has a button for door lock function (door lock part code is BYRDB5005). Got stuck with the installation? Give the Byron helpline a call and they will talk you through it. The number is on all our packaging. 3 year guarantee.