DoorKing 1812-089 Residential Only SS/Plus Face Plate

The 1812 Plus is an updated version of the 1812 Classic and features an upgraded processor, a new high fidelity digital voice circuit, better volume control, a lighted push-button and additional call out telephone numbers (up to 27).
This unique communication and access control system allows homeowners to use their existing telephone as an intercom to speak with a guest at a door or gate and is ideal for those applications requiring a basic, single door or gate, access control solution.

Manual and Technical Spec http://www.doorking.com/pages/dks-tel-1812ap.php

* Connects in series with the residential phone line. By-pass switch provided. * EEPROM Memory. * Stores up to 3 call forwarding numbers. * Full duplex commnication. * 50, 4-digit entry codes. * 24 VAC, 20 VA (250 ma) power transformer provided. * FCC (US): DUF6VT-12874-OT-0 * DOC (CAN): 1736 4507 A * Complies with UL 294; ETL Listed. * Surface mount dimensions: 6.25"H x 10"W x 5.25"D. * Flush mount dimensions: 9.25"H x 12"W x 4.5"D. * Wall mount dimensions: 7.325"H x 10.75"W x 3.5"D