Valcom's V-2904 is a Universal Four Door Intercom System. When paired with Valcom's Door Plate Speakers voice paging and handsfree talkback reply is activated for up to four doors from any telephone location. Similar to other Valcom's door entry systems, the V-2904 enables you to have the extra security you need for your organization. With a push of the button, your visitor initiates a two-way communication from the door speaker to the telephone. Once the visitor is identified then you are able to dial a code on the phone that unlocks the door.