The Elvox 6309 monitors are designed to meet any requirement for video intercom security. Surface wall mounted on a steel back plate (supplied). All monitors feature a crystal clear, hi resolution 625 lines, 4" B&W monitor, electronic tone signaling. Heavy duty coiled cord, door release, monitor activation, accessory push buttons. Brightness and color control. Door release indicator LED can be used to show status of entry doors provided with switch contacts. Other features include private conversation, restricted lock control, twisted pair operation handset with electret microphone, provides clear duplex conversation.