{
  "patent_number": "US 3906166",
  "country": "US",
  "title": "How Early Cell Phones Handled Calls Across Different Towers",
  "original_title": "Radio telephone system",
  "summary": "This patent describes a system for early portable phones to automatically find the strongest signal from a base station and switch channels as the user moves, reducing battery drain and interference.",
  "what_it_does": "This patent describes a \"portable radio telephone system\" (Claim 1) designed for mobile communication. It uses multiple base stations, each with a \"predetermined coverage area,\" that transmit on \"outgoing signalling channels\" and \"outgoing communications channels.\" Smaller \"receiver sites\" are strategically placed around these base stations to pick up signals from portable units. When a portable unit (Claim 2) needs to communicate, its \"portable receiver\" scans various \"outgoing signalling channels\" from different base stations. A \"signal strength detector\" then identifies the strongest signal, and \"logic means\" automatically tunes the \"portable transmitter\" to the correct \"incoming signalling channel\" associated with that strongest signal. For example, if you were making a call while moving between city blocks, your phone would continuously monitor which cell tower offered the best connection and seamlessly switch to it, ensuring your call remained uninterrupted.",
  "what_it_does_not_cover": [
    "Does not cover systems where the portable unit cannot automatically adjust its transmitting frequency based on the strongest received signal (Claim 2).",
    "Does not cover systems without multiple, smaller \"receiver sites\" distributed within a larger base station coverage area (Claim 1).",
    "Does not cover systems that lack a \"scanning means\" in the portable receiver to sequentially check different outgoing signalling channels (Claim 2).",
    "Does not cover systems where the base station does not compare signal strengths from its various receiver sites to determine the strongest signal from a portable unit (Claim 1).",
    "Does not cover portable units with a transmission range equal to or greater than the base station transmitter range (Claim 2)."
  ],
  "filed": "1973-10-17",
  "granted": "1975-09-16",
  "expires": "1993-10-17",
  "status": "expired",
  "holder": "Motorola Inc",
  "holder_url": "https://patentbrief.org/company/motorola-inc",
  "inventors": [
    {
      "name": "Martin Cooper",
      "url": "https://patentbrief.org/inventor/martin-cooper"
    },
    {
      "name": "Richard W Dronsuth",
      "url": "https://patentbrief.org/inventor/richard-w-dronsuth"
    },
    {
      "name": "Albert J Leitich",
      "url": "https://patentbrief.org/inventor/albert-j-leitich"
    },
    {
      "name": "Jr Charles N Lynk",
      "url": "https://patentbrief.org/inventor/jr-charles-n-lynk"
    },
    {
      "name": "James J Mikulski",
      "url": "https://patentbrief.org/inventor/james-j-mikulski"
    },
    {
      "name": "John F Mitchell",
      "url": "https://patentbrief.org/inventor/john-f-mitchell"
    },
    {
      "name": "Roy A Richardson",
      "url": "https://patentbrief.org/inventor/roy-a-richardson"
    },
    {
      "name": "John H Sangster",
      "url": "https://patentbrief.org/inventor/john-h-sangster"
    }
  ],
  "times_cited": 206,
  "tags": [
    "telecommunications",
    "consumer_electronics",
    "software",
    "semiconductors"
  ],
  "abstract": "A portable duplex radio telephone system includes at least one base station transmitter having a predetermined base transmission range, and a plurality of portable or mobile units each having a predetermined portable maximum transmission range predeterminately shorter than the base transmission range. Satellite receivers are deployed about the base station within the base station transmission range for receiving transmissions from the portable units. The base station transmitter transmits signals on a signalling channel and on at least one communications channel. Each transmitter signalling and communications channel has a frequency that is paired or associated with a receiving frequency of the satellite receivers. In a multiple base station system, the portable receiver has means for scanning the base station transmitter signalling frequencies and for tuning the portable transmitter to the signalling frequency associated with the frequency of the strongest signalling signal received from the base transmitter. When communication is initiated, the portable transmitter and receiver are automatically retuned to one of the communications channels as determined by the strongest signalling frequency received by the portable receiver and by channel availability. Means are also provided in the system to continuously locate a portable unit and switch the operating frequency thereof as the portable unit moves between base station transmitter coverage areas. Further means are provided to automatically reduce the output power of each portable transmitter to the minimum level required for satisfactory communications in order to reduce battery drain and the interference caused by the portable transmitters.",
  "url": "https://patentbrief.org/patent/us/3906166/cellular-mobile-phone-radio-telephone",
  "markdown_url": "https://patentbrief.org/patent/us/3906166/cellular-mobile-phone-radio-telephone/md",
  "google_patents_url": "https://patents.google.com/patent/US3906166",
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}