SYSTEM FOR LOCATING AND COMMUNICATING WITH MOBILE UNITS

• US 3,662,267 A
• Filed: 05/20/1970
• Issued: 05/09/1972
• Est. Priority Date: 05/20/1970
• Status: Expired due to Term

• Current Assignee: Roger R. Reed
• Original Assignee: Roger R. Reed
• Inventors: Reed, Roger R.
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US05/039,100
• Time in Patent Office: 720 Days
• Field of Search: 325/29,51,53,54,55,17 343/6.5LC,112PT
• US Class Current: 340/993
• CPC Class Codes: G08G 1/20 Monitoring the location of vehicles belonging to a group, e.g. fleet of vehicles, countable or determined number of vehicles
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

System for posting the location of each of a plurality of mobile units, for example, police cars, at a central office. The geographic area under the surveillance of the central office is divided into sectors. Each sector has a fixed pickup terminal which radiates a carrier frequency. Five different carrier frequencies are used so that each pickup terminal radiates at a frequency different from those radiated in contiguous sectors. When a mobile unit moves from one sector to another sector, it senses that the strongest carrier frequency present is that being radiated from the pickup terminal in its new sector. The mobile unit transmits its unique identification coded signal on the one of five companion carrier frequencies which corresponds to the carrier frequency radiated by the pickup terminal of the new sector. Only pickup terminals radiating a carrier frequency of the frequency of the pickup terminal in the new sector and tuned to receive the companion carrier frequency with the identification coded signal, and its strength is such that it is detected only by the pickup terminal in the new sector. The pickup terminal detects the identification coded signal and transfers it over connecting wires to the central office. The central office determines the particular mobile unit by the identification coded signal and determines its location by the particular connecting wires over which the signal is received. This data is stored in a memory at the central office, and is updated each time the mobile unit leaves one sector and enters a new sector. The system may also provide for two-way voice communication between each mobile unit and the one of several control desks at the central office to which it is assigned. Communications between a mobile unit and the pickup terminal of the sector in which it is located is by radio employing the two carrier frequencies associated with the sector. Communication from the pickup terminal to the central office is by connecting wires. When a control desk initiates a call to a particular mobile unit, the memory is searched to determine the location of the mobile unit and the control desk is connected to the proper pickup terminal.

Claims

1. A locating system for determining the location of mobile units within a geographic area comprising:

a central office;

an array of pickup terminals arranged throughout the geographic area, each pickup terminal being located within a different sector of the geographic area;

each pickup terminal including signal producing means for producing an interrogating signal which is different from the interrogating signal produced by the pickup terminals in contiguous sectors, and transmitter means for radiating the interrogating signal throughout the associated sector;

a plurality of mobile units adapted to move from sector to sector throughout the geographic area;

each mobile unit including receiver means for receiving interrogating signals from the pickup terminals in the array, detection means for selecting the interrogating signal of the pickup terminal associated with the sector in which the mobile unit is located from the interrogating signals of pickup terminals in contiguous sectors, signal producing means for producing an identifying signal containing encoded data identifying the mobile unit, and transmitter means for transmitting the identifying signal in a particular mode determined by the interrogating signal selected by said detection means when the mobile unit moves into the sector from another sector causing the detection means to select the interrogating signal from the pickup terminal associated with said sector, the particular mode of transmitting being different from the particular modes of transmitting determined by selecting of the interrogating signals radiated by pickup terminals In sectors contiguous said sector;

each of said pickup terminals also including receiver means for receiving identifying signals transmitted in the particular mode corresponding to the interrogating signal selected by a mobile unit within the sector, and connection means for transferring identifying signals to the central office over a particular path which identifies the pickup terminal; and

said central office including a memory, and control means coupled to said connection means for storing in the memory data on the mobile unit identified by a received identifying signal in association with the pickup terminal identified by the particular path over which the identifying signal is received.

2. A locating system in accordance with claim 1 wherein said signal producing means of each pickup terminal includes a frequency source for producing a frequency signal of different frequency from that produced by the pickup terminals in contiguous sectors;

each mobile unit includes a tunable frequency source for producing a carrier frequency of different frequency for each frequency signal to be selected by the detection means, and identification code modulating means for modulating the carrier frequency from the tunable frequency source with a predetermined identifying signal for identifying the particular mobile unit; and

said receiver means of each pickup terminal is operable to receive and to detect identifying signals transmitted on the particular carrier frequency corresponding to the frequency of the frequency signal transmitted by a mobile unit within the sector.

3. A locating system in accordance with claim 2 including pulsing means coupled to the array of pickup terminals for causing the pickup terminals in synchronism to radiate their associated frequency signals periodically in bursts with intervals between the bursts;

and wherein said receiver means of each mobile unit is operable to receive frequency signals from the pickup terminals in the array and to produce output signals indicative of the amplitude of the received frequency signals;

said detection means of each mobile unit is operable to receive the output signals from said receiver means and produce an output signal indicative of the frequency signal having the greatest amplitude;

each mobile unit includes control means for tuning the frequency of the tunable frequency source to a particular frequency as determined by the received frequency signal having the greatest amplitude; and

said control means of each mobile unit is operable in response to a change in the output signal of the detection means, indicating a change of received frequency signal of greatest amplitude, to cause the carrier frequency as modulated by the identification code modulating means to be transmitted during the subsequent interval between bursts.

4. A locating system in accordance with claim 3 wherein said central office includes signal receiver means for decoding said identifying signals and for providing output data designating the mobile unit identified by an identifying signal;

switching means;

switch control means connected to the switching means;

memory control means connected to the signal receiver means and to the memory; and

input control means for coupling the connection means of a pickup terminal to the switching means, the switch control means, and the memory control means in response to receiving an identifying signal transferred over the particular connection means;

said switch control means being operable to cause the switching means to connect the particular connection means to the signal receiver means in response to coupling of the particular connection means to the switch control means;

said signal receiver means being operable to receive the identifying signal when connected to the connection means by the switching means, decode the identifying signal being transferred over the connection Means, and provide output data designating the particular mobile unit identified by the identifying signal; and

said memory control means being operable to store in the memory data designating the particular mobile unit from the signal receiver means in association with data on the particular pickup terminal determined from the particular connection means coupled to the memory control means by the input control means.

5. A locating and communicating system for determining the location of mobile units within a geographic area and for providing communication between mobile units and a central office comprising a central office;

an array of pickup terminals arranged throughout the geographic area, each pickup terminal being located within a different sector of the geographic area;

a connection means between each pickup terminal and the central office;

said central office including transmission means operable to be coupled to a connection means for transferring communication signals to a pickup terminal;

each pickup terminal including signal producing means for producing an interrogating signal which is different from the interrogating signal produced by the pickup terminals in contiguous sectors, and transmitter means for radiating the interrogating signal throughout the associated sector and for radiating communication signals received from the central office throughout the associated sector in a particular mode which is different from the particular modes in contiguous sectors;

a plurality of mobile units adapted to move from sector to sector throughout the geographic area;

each mobile unit including first receiver means for receiving interrogating signals from the pickup terminals in the array, detection means for selecting the interrogating signal of the pickup terminal associated with the sector in which the mobile unit is located from the interrogating signals of pickup terminals in contiguous sectors, second receiver means connected to said detection means and operable to receive communication signals in the particular mode radiated by the pickup terminal radiating the interrogating signal selected by the detection means, transmitter means connected to the detection means for transmitting in a particular mode determined by the interrogating signal selected by said detection means, the particular mode of transmitting being different from the particular modes of transmitting determined by selecting of the interrogating signals radiated by pickup terminals in sectors contiguous said sector, identification signal producing means for producing an identifying signal containing encoded data identifying the mobile unit, communication signal producing means for producing communication signals, means connected to the detection means and operable to couple the identification signal producing means to the transmitter means when the mobile unit moves into the sector from another sector causing the detection means to select the interrogating signal from the pickup terminal associated with said sector, thereby enabling the transmitter means to transmit the identifying signal in the particular mode, and means selectively operable to couple the communication signal producing means to the transmitter means thereby enabling the transmitter means to transmit communication signals in the particular mode;

each of the pickup terminals also including receiver means for receiving signals transmitted in the particular mode corresponding to the interrogating signal selected by a mobile unit within the sector and for coupling the signals to the connection means between the pickup terminal and the central office; and

said central office also including a memory, control means coupled to said connection means for storing in the memory data on the mobile unit identified by a received identifying signal in association with the pickup terminal identified by the pArticular connection means over which the identifying signal is received, and communication signal receiver means operable to be coupled to a connection means for receiving communication signals.

6. A locating and communicating system in accordance with claim 5 wherein each pickup terminal includes a frequency source for producing a frequency signal of different frequency from that produced by the pickup terminals in contiguous sectors, the frequency signal serving as an interrogating signal, and modulator means connected to the connection means and to the frequency source and operable to modulate the frequency signal with communication signals from the central office, each mobile unit includes a tunable frequency source for producing a carrier frequency of different frequency for each frequency signal to be selected by the detection means, identification code modulating means for modulating the carrier frequency from the tunable frequency source with a predetermined identifying signal for identifying the particular mobile unit, and communication signal modulating means for modulating the carrier frequency source with communication signals;

and said receiver means of each pickup terminal is operable to receive and to detect signals transmitted on the particular carrier frequency corresponding to the frequency of the frequency signal transmitted by a mobile unit within the sector.

7. A locating and communicating system in accordance with claim 6 including pulsing means coupled to the array of pickup terminals for causing the pickup terminals in synchronism to radiate their associated frequency signals periodically in bursts with intervals between bursts;

and wherein said first receiver means of each mobile unit is operable to receive frequency signals from the pickup terminals in the array and to produce output signals indicative of the amplitude of the received frequency signals;

said detection means of each mobile unit is operable to receive the output signals from said first receiver means and produce an output signal indicative of the frequency signal having the greatest amplitude; and

each mobile unit includes control means for tuning the frequency of the tunable frequency source to a particular frequency as determined by the received frequency signal having the greatest amplitude.

8. A locating and communicating system in accordance with claim 7 wherein each mobile unit includes signaling modulating means for modulating the carrier frequency from the tunable frequency source with a predetermined calling signal for identifying the particular mobile unit, and means selectively operable to couple the signaling modulating means to the transmitter means thereby enabling the transmitter means to transmit calling signals;

and said central office includes signal receiver means for decoding said identifying signals and said calling signals and for providing output data designating the mobile unit identified by the signals and further providing output data indicating the presence of a calling signal, a plurality of control units, each control unit having assigned thereto certain ones of the plurality of mobile units, switching means, switch control means connected to the switching means, memory control means connected to the memory, input control means for coupling the connection means from a pickup terminal to the switching means, the switch control means, and the memory control means in response to receiving a signal over the particular connection means, said switch control means being operable to cause the switching means to connect the particular connection means to the signal receiver means in response to coupling of the particular connection means to the switch control means, said signal receiver means being operable to receive identifying signals and calling signals when connected to the connection means by the switching mEans, decode the signal, provide output data designating the particular mobile unit identified by the signal, and further provide output data indicating the presence of a calling signal, signal selector means connected to the signal receiver means and the memory control means and operable to transfer output data designating the mobile unit identified from the signal receiver means to the memory control means when the data does not indicate the presence of a calling signal, said memory control means being operable to store in the memory data designating the particular mobile unit from the signal selector means in association with data on the particular pickup terminal determined from the particular connection means coupled to the memory control means by the input control means, allocation means connected to the signal selector means and to the switch control means and having stored therein data on the certain ones of the mobile units assigned to each control unit, said allocation means being operable to transfer to the switch control means the designation of the particular control unit associated with the particular mobile unit identified by the output data from the signal receiver means when the data from the signal selector means indicates the presence of a calling signal, said switch control means being operable to cause the switching means to disconnect the particular connection means from the signal receiver means and connect the particular connection means to the particular control unit in response to data from the allocation means identifying the control unit, location lookup means connected to the switch control means and to the memory, call signaling means connected to the location lookup means and to the control units and operable to enable a control unit to provide a call signal at the location lookup means identifying a particular mobile unit to be called, said location lookup means being operable to search the memory and determine the particular pickup terminal associated with the mobile unit identified by the call signal and transfer to the switch control means the designation of the particular pickup terminal, and said switch control means being operable to cause the switching means to connect the particular control unit to the connection means for the particular pickup terminal identified by the call signal.