This product enables office personnel to talk directly with visitors prior to their entering a business. When a visitor presses the Call Button, the system rings the designated phone(s) in an office and allows two-way conversation. The optional Door Opening Controller enables any Norstar phone to control a latch on a door or a gate. It allows two-way conversation between the Norstar phone and the Doorphone.It can be located up to 2600 feet away from the main system with optional SAP. It requires 1 unused station port, can ring one or multiple stations, can be used in conjunction with DOC for door strike operations, can be answered by voicemail, and up to 4 doorphones per system can be installed compatible with all releases.