Object locator system employing variable frequency code tone generators

• US 4,224,596 A
• Filed: 03/21/1975
• Issued: 09/23/1980
• Est. Priority Date: 03/21/1975
• Status: Expired due to Term

• Current Assignee: Elwyn R. Knickel
• Original Assignee: Elwyn R. Knickel
• Inventors: Knickel, Elwyn R.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Groody, James J.
• Application Number:
  US05/560,811
• Time in Patent Office: 2,013 Days
• Field of Search: 340/24, 340/32, 340/23, 340/62, 340/263, 340/52 R, 340/53, 340/171 PF, 340/350, 340/351, 179/2 DP, 343/112 PT, 325/6, 325/47, 325/55, 235/150.26, 235/150.27, 235/30 R, 324/167, 364/444, 364/449, 364/460
• US Class Current: 340/992
• CPC Class Codes: G08G 1/127 to a central station ; Indicators in a central station
• 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

Abstract

Improvements are provided for a vehicle locator system of the type in which vehicle-borne emitters radiate coded tone combinations for reception by spaced sensors which are linked to a central decoding office. In one improvement the vehicle capacity of the system is increased without increasing the number of tone oscillators by using a sequential tone coding arrangement wherein each oscillator is switchable to provide a different tone during different intervals in the coding sequence. In addition, the pulsing rate of the emitted tone is synchronized to the vehicle odometer to assure that a code sequence is transmitted while the vehicle is in the proximity of each sensor station. Additional modifications include party line sharing of telephone lines connecting the sensors to the decoder, the use of long-distance telephone connections to provide coverage for large geographie regions, the use of radio call boxes to link the sensors to a decoding station, and delaying emitter pulsing when two vehicles are in close proximity to reduce the possibility of simultaneous reception of two vehicle codes at a sensor station.

Claims

1. In a system for monitoring the location of movable objects relative to multiple prescribed locations:

an emitter carried by each movable object for automatically transmitting coded signals uniquely identifying that movable object, transmission from said emitters being at some nominal power level;

a plurality of sensor stations, at least one at each of said prescribed locations, each sensor station being arranged to receive signals from an emitter located within a predetermined distance from that sensor station, said prescribed locations being spaced sufficiently to prevent the signal transmitted by an emitter at said nominal power level from being received at more than one sensor station at a time;

a central processing station; and

means for automatically transferring received coded signals and sensor station location signals from said sensor stations to said central processing station;

wherein each emitter is characterized by the transmission of code tones during plural successive intervals, plural code tones being transmitted simultaneously during each interval, each emitter including;

a plurality of oscillators for providing code tones;

actuable control means for switching the frequency of at least one of said oscillators between plural discrete frequencies;

timing means for defining said plural intervals;

with pre-established time durations

transmitter means responsive to said timing means for transmitting said code tones simultaneously during at least two successive intervals of said plural intervals; and

means responsive to said timing means for actuating said control means to change the frequency of said at least one oscillator from one to the other of said two successive intervals.

2. The system according to claim 1 wherein said at least one oscillator operates at the same frequency during the first of said successive intervals in each emitter, said same frequency identifying said first of said successive intervals.

3. The system according to claim 2 wherein all of said oscillators are arranged to have their frequencies switched by said control means in said two successive intervals.

4. The system according to claim 1 wherein the combined code tones transmitted during at least one of said intervals represent the identity of the movable object from which the tones are transmitted, and wherein the combined code tones transmitted during at least another of said intervals represent a condition associated with the movable object from which the tones are transmitted.

5. The system according to claim 1 wherein said movable objects are motorized vehicles each having an odometer, each odometer including a movable member which moves at a rate proportional to vehicle speed, and wherein said transmitter means includes logic means responsive to said movable odometer member for repetitively transmitting said sequence of code tones at a repetition rate determined by the rate of movement of the movable member.

6. The system according to claim 5 wherein said movable member comprises an odometer cable arranged to rotate in response to movement of said vehicle, and wherein said logic means comprises:

means for generating a count pulse for each complete rotation of said odometer cable;

divider means for counting each count pulse and providing an actuator pulse each time a predetermined number of count pulses is counted; and

gating means for gating on said transmitter means in response to said actuator pulse.

7. The system according to claim 6 further comprising means for periodically gating on said transmitter means in response to a predetermined time delay between successive actuator pulses.

8. The system according to claim 1 wherein said sensor stations are connected to said central processing station via respective telephone lines used solely for transmission of signals between said central processing station and a respective sensor station.

9. The system according to claim 1 wherein said sensor stations are connected to said central processing station via telephone party lines.

10. The system according to claim 1 wherein said sensor stations communicate with said central processing station via long distance telephone lines, wherein each sensor station includes:

means for temporarily storing received code tones;

means responsive to reception of code tones for automatically attempting to establish connection to said central processing station on said long distance telephone lines; and

means responsive to establishment of said connection for transmitting the temporarily stored code tones to said central processing station via said established connection on said long distance telephone lines.

11. The system according to claim 1 wherein said sensor stations communicate with said central processing station via a radio channel, said sensor stations each including:

a radio transmitter tuned to said channel; and

means responsive to reception of code tones for actuating said radio transmitter to transmit said code tones to said central processing station.

12. The system according to claim 1 further characterized in that said transmitter means is inhibited from transmitting code tones when its emitter is proximate a further emitter having a further transmitter means which is in the process of transmitting code tones, each emitter including:

a blanking transmitter for transmitting a blanking pulse when said transmitter means is transmitting code tones;

a blanking pulse receiver for receiving blanking pulses transmitted from other emitters which are located within a predetermined distance from said each emitter; and

delay means for inhibiting said transmitter means for a period of time greater than the duration of said plural successive intervals.

13. In a vehicle locator system of the type in which vehicles carry emitters which transmit code signals for reception at individual sensor stations dispersed throughout a prescribed area or route, vehicle speedresponsive apparatus associated with each emitter for assuring that a vehicle passing a sensor station transmits said code signals at least once while in the receiving range of the passed sensor station, said apparatus comprising:

an odometer cable;

pulsing means for sensing rotation of said odometer cable and providing a gating pulse for every n rotations of said odometer cable, where n is greater than one; and

gating means responsive to each gating pulse for actuating said emitter to transmit said code signals.

14. The system according to claim 13 further comprising means responsive to elapse of at least a predetermined period of time between successive gating pulses for actuating said emitter to transmit said code signals.

15. The system according to claim 13 wherein each emitter includes:

a plurality of code tone oscillators, each switchable to operate at least at two frequencies;

timing means for dividing the transmission of code tones into at least two intervals; and

means for switching the frequencies of said oscillators so that each operates at two different frequencies in said two intervals, respectively.

16. A vehicle identification system of the type in which vehicles carry emitters for transmitting code signals to sensor stations spaced along a prescribed route or within a prescribed geographic area, said system being characterized in that said sensor stations communicate with a central processing station via long distance public telephone lines, said system including:

at said sensor stations;

means for detecting when code signals have been received from a vehicle emitter;

means for temporarily storing the received code signals until they are transmitted to said central processing station;

means responsive to detection of received code signals for automatically dialing said central processing station on said long distance public telephone lines to attempt to establish a long distance telephone connection between said sensor station and central processing station; and

means responsive to establishment of a long distance telephone connection between said sensor station and said central processing station for transmitting the temporarily stored code signals to said central processing station via said long distance public telephone lines.

17. The system according to claim 16 further comprising, at each sensor station, delay means for delaying automatic dialing for a predetermined period after received code signals are detected to permit code signals from other nearby vehicle emitters to be temporarily stored and transmitted to said central processing station during a common long distance connection.

18. The system according to claim 17 further comprising, at each sensor station, auxiliary means for temporarily storing code signals received from vehicles while a long distance transmission of previously-received code signals is in progress;

wherein said means for automatically dialing is responsive to storage of code signals in said auxiliary means at the termination of a long distance call for automatically dialing said central processing station to establish a long distance connection therewith.

19. The system according to claim 16 wherein each emitter includes:

a plurality of oscillators for providing code tones;

actuable control means for switching the frequency of said oscillators between plural discrete frequencies;

timing means for defining plural successive time intervals;

transmitter means responsive to said timing means for combining and transmitting said code tones during at least a portion of each of said intervals; and

means responsive to said timing means for actuating said control means to change the frequency of said oscillators in different intervals.

20. In a system for monitoring the location of movable objects relative to multiple prescribed locations:

an emitter carried by each movable object for automatically transmitting coded signals uniquely identifying that movable object, transmission from said emitters being at some nominal power level;

a plurality of satellite sensor stations, at least one at each of said prescribed locations, each satellite sensor station being arranged to receive signals from an emitter located within a predetermined distance from that satellite sensor station, said prescribed locations being spaced sufficiently to prevent the signal transmitted by an emitter at said nominal power level from being received at more than one satellite sensor station at a time;

a plurality of main sensor stations, each associated with a respective group of said satellite sensor stations;

radio transmitter means in each satellite sensor station for transmitting coded signals received by said satellite sensor station to the main sensor station associated therewith;

radio receiver means at each main sensor station for receiving coded signals transmitted from satellite sensor stations associated with that main sensor station;

a central processing station; and

means at each main sensor station for automatically transferring coded signals received from said satellite sensor stations to said central processing station.

21. The system according to claim 20 wherein the last-mentioned means includes telephone lines.

22. The system according to claim 20 wherein the last-mentioned means comprises:

means responsive to reception of coded signals from said satellite sensor stations for automatically dialing said central processing station via public telephone lines to attempt to establish telephone contact between said main sensor station and said central processing station; and

means responsive to establishment of said telephone contact for transmitting the coded signals received at said main sensor station to said central processing station.