Viewing and oral communications assembly for doors
Patent 4763444 Issued on August 16, 1988. Estimated Expiration Date: 
June 30, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
June 30, 2007. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 141476 425500 584078 1799164 1901303 2096740 2624922 3203052 Security viewing device Observation port assembly InventorApplicationNo. 07/068258 filed on 06/30/1987US Classes:49/171, Viewing, ventilating, or packet passage359/511, Cap or cover359/839, With a transmitting property359/850, Plural mirrors or reflecting surfaces359/894OPTICAL APERTURE OR TUBE, OR TRANSPARENT CLOSUREExaminersPrimary: Kannan, Philip C.Attorney, Agent or FirmInternational ClassesE06B 7/00 (20060101)E06B 7/30 (20060101) AbstractA viewing and oral communications assembly for doors generally rectangular in shape, having mirror surfaces to transmit images from positions adjacent to the door through the assembly and having audio communication slots which are closed by expansion of intumescent material in the presence of heat.Other References
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