The Aiphone LEF-3 Open Voice selective-call master intercom works with any combination of up to three Aiphone LAF and LEF Series master intercoms or LA, LE, and LS Series door and sub-master intercoms (sold separately) to enable audio communication with a visitor at a door and with other rooms within the building. Three buttons with LED indicators allow the master intercom to direct a call and communicate with the desired door or sub-master intercom. Calls received from a sub-master intercom are indicated by a momentary chime and the corresponding LED indicator above the selectable buttons illuminating for 20 seconds. Depressing the push-to-talk button on the master intercom allows the user to talk to the specified door or sub-master intercom user, and releg the button immediately transmits sound from the door or sub-master intercom to the master intercom. The privacy button prevents other intercom users in the system from overhearing a conversation with another intercom. At any time, the master user can listen to audio transmissions from a specified door or sub-master intercom. The chime and audio volume is adjustable, and switching the power button to off silences the master intercom's chime alerts. The housing is white plastic and mounts to a desktop or wall using the included mounting hardware. The system is hardwired to be powered by a 12V power supply (sold separately). SpecificationsOverall dimensions7-1/6 x 5-5/8 x 2-1/8 inches (H x W x D)*Communication output500 mWPower requirementsAiphone PS-1225UL 12V power supply (sold separately)*H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back. Door intercom systems allow an occupant of a building to communicate remotely with a visitor through at least one door intercom and master intercom. Master intercoms with a door-access button remotely unlock the door for the visitor. Aiphone manufactures intercom systems for residential, business, and healthcare structures. The company, founded in Japan in 1948, has its North American headquarters in Bellevue, WA. Aiphone meets International Organization for Standardization (ISO) standards 9001 and 14001. WHAT'S IN THE BOX? * Aiphone LEF-3 master intercom * Mounting hardware * Instructions

Adjustable chime and audio volume. Listening feature allows the master intercom operator to receive audio transmission from a door or sub-master intercom at any time. Privacy button prevents other intercom users in the system from overhearing a conversation with another intercom. Three buttons with LED indicators allow the master intercom operator to direct a call and communicate with the desired door or sub-master intercom. Master intercom works with any combination of up to three door, sub-master, or master intercoms (sold separately) to enable audio communication with visitors and other rooms within the building.