Differential stethoscope
Patent 4438772 Issued on March 27, 1984. Estimated Expiration Date: 
April 8, 2002. 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.
April 8, 2002. 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 ReferencesInventorAssigneeApplicationNo. 06/366516 filed on 04/08/1982US Classes:600/528, Detecting heart sound381/67STETHOSCOPES, ELECTRICALExaminersPrimary: Cohen, Lee S.Assistant: Jaworski, Francis J. Attorney, Agent or FirmInternational ClassesA61B 7/00 (20060101)A61B 7/04 (20060101) AbstractA portable differential stethoscope includes small microphone elements which are attached to the stethoscope heads to pick up acoustic signals from the body. The sounds picked up by the stethoscope heads include body noise signals as well as heartbeat signals. Each stethoscope head and microphone element provides an output which is amplified in an individual amplifier. The two amplified signals are inputted to separate terminals of a differential amplifier through a gain and balance control element. The differential amplifier outputs a difference signal which is amplified and inputted to an electrical headset or an electrical earphone element which is acoustically coupled to the conventional acoustic tube.Other References
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