Invalidity dossier
US 5228074
Dual mode cellular telephone apparatus
Current assignee: Sony Electronics Inc
Added 9/23/2026, 7:15:29 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview: US5228074A — Dual Mode Cellular Telephone Apparatus
Title: Dual mode cellular telephone apparatus
Patent number / application: US5228074A; application US07/684,774
Inventor: Semyon Mizikovsky
Assignee (per source): Original assignee Sony Corp; a 1991-04-15 assignment records Sony Corporation of America (Park Ridge, NJ), and an August 23, 1993 reassignment records Sony Electronics Inc. The source notes listed assignees may be inaccurate and that no legal analysis was performed.
Key dates: Priority/filing date 1991-04-15; publication (grant) date 1993-07-13; anticipated expiration 2011-04-15. Legal status listed as "Expired - Lifetime."
Purpose and plain-language scope: The invention relates to cellular telephone apparatus that can operate in both analog and digital modes. Conventional analog mobile stations transmit analog voice signals (e.g., FM) on a carrier. The dual mode standard identified in the text as TIA IS-54 permits voice to be sent in analog or digital form; digital techniques improve voice quality and increase the number of simultaneous users, and the system may carry data beyond voice.
The stated problem is that adding dual analog/digital capability to a mobile unit normally makes it large, heavy, and no longer hand-held portable. The proposed apparatus separates the electronics: a portable unit communicates substantially only in analog mode and can operate as a self-contained, hand-held unit (keypad 3, display 4, low-gain antenna 11, microphone 40, speaker 45). A mobile unit 5 — intended for a vehicle and including an adapter 7 and a digital communications unit (DCU) 8 — communicates in both analog and digital modes. Mating contacts 2 and 6 connect the units and can let the vehicle battery 9 power the portable unit, which may also have a rechargeable battery. When connected, a controller routes voice signals from the portable unit's microphone through the mobile unit to a base station, and received analog or digital signals back to the portable unit's speaker; the base station determines the mode via control signals. Controllable switching selects portable and mobile portions for each mode.
Source: https://patents.google.com/patent/[US5228074](/patent/US5228074)/en
What the excerpt does not establish: It is an excerpt with text omitted; the full claims, complete specification, all drawing details, and the actual prior-art references are not shown. It does not establish validity, enforceability, current ownership, litigation history, or the accuracy of the listed assignees or legal status.
Generated 10/1/2026, 9:42:15 PM
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Litigation summary
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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