Specifications Used as an intercom to control access to your building. Pressing the Call button on the BST Doorphone calls one or more telephones or sends a distinctive chime to telephones in an assigned page zone or both Can add optional Door Opening Controller (DOC), controlled by pressing softkey Installed and programmed like any M7000 or T7000 digital phone Up to four Doorphones accommodated on a Norstar system Compatible with 3x8 DR5, Compact DR2, DR5, DR5-DS, Modular DR2-DR5, Norstar CICS, MICS, and BCM digital station ports.