Transponder distinction in a fueling environment

The present invention relates to a fuel dispenser having a fuel delivery path, a pump associated with the delivery path for pumping fuel from a storage tank to a fueling nozzle and a controller and communication system adapted to receive remotely transmitted signals from transmitters of different types. The controller is adapted to determine the type of transmitter from which the remotely transmitted signals were received, and preferably, whether or not the transmitter is moved with respect to the dispenser. The controller and communication depending on the sophistication of the system or respond to information in the transmitted signals indicating the vehicle is moving.

BACKGROUND OF THE INVENTION 
This application claims the benefit of U.S. Provisional application No. 
60/060,066, filed Sep. 26, 1997. 
The present invention relates generally to fuel dispensers and, more 
particularly to fuel dispensers capable of distinguishing between various 
types of transponders capable of communicating with the dispenser and 
detecting movement of the transponder within and throughout the fueling 
environment. 
In recent years, traditional gasoline pumps and service stations have 
evolved into elaborate point-of-sale (POS) devices having sophisticated 
control electronics and user interfaces with large displays and touch-pads 
or screens. The dispensers include various types of payment means, such as 
card readers, to expedite and further enhance fueling transactions. A 
customer is not limited to the purchase of fuel at the dispenser. More 
recent dispensers allow the customer to purchase services, such as car 
washes, and goods, such as fast food or convenience store products at the 
dispenser. Once purchased, the customer need only pick up the goods and 
services at the station store or the outlet of a vending machine. 
Remote transaction systems have evolved wherein the fuel dispenser is 
adapted to communicate with various types of remote communication devices, 
such as transponders, to provide various types of identification and 
account information to the fuel dispenser automatically. Given the 
sophistication of these transaction systems and the numerous choices 
provided to the customer at the dispenser, distinguishing between 
transponders carried on a person and transponders mounted in a vehicle 
will be useful to allow the dispenser and fuel station store to monitor 
the movement of a person carrying a transponder and a vehicle having a 
transponder. Monitoring such movement would allow the fueling system to 
prevent drive-offs during a fueling operation wherein the dispenser's 
nozzle is still in the fill neck of the vehicle's fuel tank. The 
additional merchandising options provided to the customer may increase the 
risk of drive-offs. For example, in a single visit to a service station, a 
customer may fuel the vehicle and pay for the fuel dispensed at the fuel 
dispenser and order food at an associated quick-serve restaurant. During 
fueling, the customer may decide to pick up the ordered food and purchase 
other goods in the convenience store. Given all the transactions 
available, the customer could easily forget to complete the fueling 
transaction by replacing the dispenser nozzle back in the dispenser 
housing, or in cases where payment at the pump was not made, the customer 
could forget to pay for the fuel and drive off believing the fuel is paid 
for when in actuality only the convenience store products or fast food was 
actually purchased. In other situations, customers may intend on driving 
off without paying for the fuel. Given the increased volume of 
transactions occurring at the dispenser, it is difficult to keep track of 
and notice a customer driving off without paying for the fuel. In any of 
these and other related situations, keeping track of a vehicle using a 
vehicle mounted transponder may prevent intentional and unintentional 
drive-offs without paying or completing the fueling transaction. 
Keeping track of a person or vehicle throughout the fuel station 
environment may be beneficial in other applications, such as advertising 
and merchandising. Given the projected mixture of both personal and 
vehicle mounted transponders, distinguishing between the types of 
transponders is desirable in certain applications to allow persons 
carrying a transponder to leave the immediate fueling position at the fuel 
dispenser during the fueling operation while preventing or limiting 
movement of a vehicle during the fueling operation to prevent drive-offs 
as well as monitor movement of person having personal transponders. 
Thus, there is a need for a fuel dispensing system capable of determining a 
type of transponder in addition to being able to determine movement of 
certain of these transponders to enhance security, safety and 
functionality of modern fueling environments. 
SUMMARY OF THE INVENTION 
The present invention fulfills this need by providing a fueling system 
capable of distinguishing between types of remote communication devices 
(generally referred to as transponders) based on the signals transmitted 
from the transponder, such as the type of signals transmitted or 
information transmitted therein. The transmitted signals may originate at 
the transponder or be a modification of signals originally transmitted to 
the transponder. Based the type of transponder, the system may control 
dispenser functions differently. For example, certain applications may 
allow transponders carried on a person to be moved about the fueling 
environment during a fueling operation, but stop fueling and provide 
warning or instructional information if a vehicle mounted transponder 
begins or starts to move during the fueling operation. Vehicle 
transponders may also interface with the vehicle's control system or bus 
network to disable the vehicle and prevent movement. 
The fueling system may use many different types of techniques to determine 
transponder movement within the fueling environment, and in particular, 
with respect to the fuel dispenser at which the fueling operation is 
taking place. The system may simply determine a relative change in the 
proximity of the transponder with respect to the dispenser, determine a 
change in location with respect to the dispenser or simply receive data 
from the vehicle transmitter or other remote source indicating the vehicle 
is moving or preparing to move. Preferably, in the latter situation, the 
vehicle transmitter is associated with a vehicle control system capable of 
sending information to the transmitter indicative of the vehicle being 
started, placed in gear and/or actually moving. In certain situations, a 
global positioning system may be used to interact through the vehicle or 
part of the fueling system to provide information on vehicle movement and 
location. 
Accordingly, a fuel dispenser is disclosed having a fuel delivery path, a 
pump associated with the delivery path for pumping fuel from a storage 
tank to a fueling nozzle and a controller and communication system adapted 
to receive remotely transmitted signals from transmitters of different 
types. The controller is adapted to determine the type of transmitter from 
which the remotely transmitted signals were received, and preferably, 
whether or not the transmitter is or is about to be moved with respect to 
the dispenser. The controller and communication electronics may rely on 
varying signal characteristics to determine proximity or location 
depending on the sophistication of the system or respond to information in 
the transmitted signals indicating the vehicle is moving. 
The controller may be associated with one or more antennas placed anywhere 
within the fueling environment, including within or one or more 
dispensers. The signals received at one or more of these antennas may be 
monitored to determine changes in signal characteristics indicative of 
movement of the transmission source. For example, determining proximity 
changes may include monitoring signal strength, magnitude or changes in 
phase. Using multiple antennas and known locating techniques, such as 
triangulation, based on signal characteristics received at each antenna, 
the location and movement of transmitters and items or persons associated 
therewith may be tracked or monitored for movement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following description, like reference characters designate like or 
corresponding parts throughout the several figures. It should be 
understood that the illustrations are for the purpose of describing 
preferred embodiments of the invention and are not intended to limit the 
invention thereto. 
As best seen in FIG. 1, a fuel dispenser, generally designated 10, is shown 
constructed according to the present invention. The fuel dispenser 
provides a fuel delivery path from an underground storage tank (not shown) 
to a vehicle 200 (shown in FIGS. 2 and 3). The delivery path includes a 
fuel delivery line 12 having a fuel pump/metering device 14. A fuel 
delivery line 12 communicates with a fuel delivery hose 16 outside of the 
dispenser 10 and a delivery nozzle 18. The nozzle 18 provides manual 
control of fuel delivery to the vehicle 200. 
The dispenser 10 also includes a control system having a dispenser 
controller 20 and associated memory 22. The controller may receive volume 
data from the pump/meter device 14 through cabling 24 as well as provide 
control of fuel delivery. The dispenser controller 20 may provide audible 
signals to an audio module and speaker 26 in order to provide various 
beeps, tones and audible messages to an operator. These messages may 
include warnings, instructions and advertising. 
The dispenser 10 may include a card reader 28 or a cash acceptor 30 and a 
receipt printer 32. With these options, the dispenser controller 20 may 
read data from the magnetic strip when a card is inserted in the card 
reader 28 and communicate to a service-station-based controller 34 (as 
shown in FIG. 2), such as the G-site controller sold by Gilbarco, Inc. of 
Greensboro, N.C. The service station based controller 34 generally 
communicates with a remote credit card verification authority to ascertain 
whether a transaction proposed to be charged to or debited from the 
account associated with the card inserted in the card reader 28 is 
authorized. 
The dispenser 10 may also include various types of displays, preferably, 
one or more alpha numeric displays 36 in addition to a high resolution 
graphics display 40. Preferably, the graphics display 40 will have an 
associated graphics display keypad 42 adjacent the display or integrated 
with the graphics display 40 to provide a touch screen interface. The 
dispenser may include an additional general keypad 44. Notably, the 
displays 36, 40 and keypads 42, 44 may be integrated into a single device. 
The controller 20 is desirably comparable to the microprocessor based 
control systems used in CRIND (card reader in the dispenser) and TRIND 
(tag or transponder reader in the dispenser) type units sold by Gilbarco, 
Inc. under the trademark THE ADVANTAGE. 
The dispenser controller 20 will have or be associated with communication 
electronics 46 for providing remote unidirectional or bidirectional 
communications between a transponder and the dispenser. The transponders 
may be passive or active, depending on the desired functionality and 
application, and is intended to include remote communication devices 
independently generating a transmission signal as well as those adapted to 
modify received signals for transmission back to the dispenser. In short, 
the transponder (or remote communication unit) is capable of communicating 
information in any remote manner to the dispenser communication 
electronics 46. The transponder may operate to transmit and receive 
signals as typical with transmitters and receivers or modify signals 
received in order to communicate information without actually generating a 
new transmission signal. The transponder may incorporate the Micron 
MicroStamp.TM. produced by Micron Communications, Inc., 8000 South Federal 
Way, Boise, Id. 83707-0006. The Micron MicroStamp engine is an integrated 
system implementing a communications platform referred to as the 
MicroStamp standard on a single CMOS chip. A detailed description of the 
MicroStamp engine TM and the method of communication is provided in its 
data sheets and the MicroStamp Standard Programmers Reference Manual 
provided by Micron Communications, Inc. These references and the 
information provided by Micron Communication on their web site at 
HTTP://WWW.MCC.MICRON.COM are incorporated herein by reference. 
The remote communication electronics sending or modifying a signal 
originating from the dispenser is generally referred to as a transmitter. 
In short, "transmitter" is intended to encompass both traditional 
transponder and independent transmitter embodiments. Communications may 
include RF, infrared, acoustic or other known remote communication methods 
acceptable for use in a fueling environment. The dispenser associated 
communications electronics 46 may include a receiver, transmitter or an 
integrated transceiver to perform such remote communications. Preferably, 
the communications electronics 46 take the form of an interrogator. The 
communication electronics 46 include or are associated with any number of 
antennas located in or around the dispensers and fueling environment. In 
particular, these antennas may include a dispenser antenna 52, a store 
antenna 54 located on or near the fuel station store 48 or an area antenna 
56 located anywhere throughout the forecourt or fueling environment around 
the fuel station store 48, as depicted in FIG. 2. The communications 
electronics 46 may be associated with any one or more of these various 
types of antennas 52, 54, 56. 
In operation, a customer 100 will drive into the fueling environment and up 
to a fuel dispenser 10 in the vehicle 200. Depending on the type of remote 
communications unit or transponder, the vehicle 200 may be equipped with a 
vehicle transponder 202. The person may be carrying a personal transponder 
102 or both the vehicle 200 and the person 100 may have their respective 
transponders 202, 102. The controller 20, in association with the 
communication electronics 46 is adapted to determine the type of 
transponder (personal transponder 102 or vehicle transponder 202) based on 
data transmitted or the type of signal transmitted to the dispenser 10. 
Regardless of how the determination is made, the controller 20 determines 
the type of transponder and provides an output if a vehicle transponder 
202 is detected and attempts to move during a fueling operation. If a 
personal transponder 102 is detected, the controller may not provide an 
output if movement of the person 100 is detected. 
The invention prevents accidental drive-offs during a fueling operation by 
shutting off fuel delivery, providing an audible announcement through the 
audio module and speaker 26, disabling the vehicle or a combination 
thereof. The fueling operation may include the actual delivery of fuel as 
well as any time after fueling is completed to ensure proper payment for 
fuel or other goods and services, is or has been made. Thus, the system 
acts to prevent accidental and intentional drive-offs which could result 
in damage to the dispenser equipment and persons in the fueling 
environment as well as theft of fuel. 
In short, the controller 20 allows for movement of personal transponders 
102 throughout the fueling environment during a fueling operation, but 
provides an alert or control function when movement or a specific amount 
of movement by a vehicle mounted transponder 202 is detected during the 
fueling operation. 
A few of the numerous possibilities for transponder type and location are 
shown in FIGS. 3A-3C. FIG. 3A depicts a vehicle 200 having the vehicle 
mounted transponder 202, while FIGS. 3B and 3C depict a personal-type 
transponder 102 integrated within a debit, credit or smartcard 104 and a 
key fob 106. The transponders 102, 202 may take any number of forms to 
facilitate the inventive concept disclosed herein. 
Attention is directed to the flow chart shown in FIG. 4 wherein the 
controller 20 and communication electronics 46 begin by monitoring for the 
presence of a personal transponder 102 or a vehicle transponder 202 (block 
300). Once the controller 20, in conjunction with the communications 
electronics 46, detects and begins communication with a transponder 102, 
202 (block 302), the controller 20 determines the type of transponder, 
either personal 102 or vehicle 202 (block 304), by monitoring the type or 
characteristics of the signals transmitted from the transponder 102, 202 
or by reading information transmitted by the signals. The transponder and 
controller are, of course, pre-configured to use one or more of these 
methods. 
Depending on the application, the controller 20 may send out continuous or 
periodic signals for a transponder 102, 202 to respond to. The transponder 
102, 202 may send back a specific type of signal or information on a 
carrier signal to alert the controller 20 that a transponder is within the 
range of communications. In such cases, the transponder may respond with a 
separate signal or modify the signal emanating from the controller 20 in a 
manner detectable by the controller 20. In other situations, the 
transponder 102, 202 may initiate transmission by transmitting periodic or 
continuous signals for the controller 20 to detect when the transponder is 
within a proximity capable of carrying out communications. Attention is 
drawn to patent application Ser. No. 08/759,733, filed Dec. 6, 1996 and 
assigned to Gilbarco, Inc., the disclosure of which is incorporated herein 
by reference. The controller 20 next monitors for the beginning of a 
fueling operation (block 306). Once the fueling operation begins, the 
controller 20 monitors for movement of the vehicle transponder 202 with 
respect to the fuel dispenser 10. Preferably, if the transponder is a 
personal transponder 102 and not a vehicle transponder 202, the controller 
will not monitor to determine movement with respect to the dispenser 10 
(block 308) and will end monitoring of transponder movement (block 318). 
However, certain applications may require monitoring of the personal 
transponder 102 and person 100 throughout the fueling environment and fuel 
station store 48. 
If the fueling operation has begun and the transponder is a vehicle 
transponder 202 (block 308), the controller 20 will monitor signals 
transmitted from the vehicle transponder 202 to determine if the vehicle 
is moving or is about to be moved (block 310). If the controller does not 
detect movement of the vehicle 200 or vehicle transponder 202 (block 312), 
the controller 20 will determine if the end of the fueling operation has 
occurred (block 314). If the fueling operation is not at an end, the 
controller 20 will continue monitoring to determine if the vehicle is or 
is about to be moved (block 310). If the vehicle has moved (block 312), 
the controller 20 determines if the fueling operation has ended (block 
316). If the fueling operation is at an end, the controller may end the 
monitoring process (block 318). If the fueling operation is not at an end, 
the controller 20 will stop fueling, provide an instructional or warning 
announcement (block 320). The controller 20 may continue to monitor 
movement and continue fueling and/or control the warning or instructional 
announcement if movement stops or as the situation dictates. The process 
will generally continue until the end of the fueling operation. In certain 
applications, for example, where additional goods or services have been 
purchased, transponder monitoring may continue until the customer leaves 
the fueling environment. 
The controller 20 operating in conjunction with the communication 
electronics 46 may determine movement of a transponder 102, 202 by 
detecting a change in relative proximity of the transponder 102, 202 with 
respect to the fuel dispenser 10, by detecting a change in location of the 
transponder 102, 202 with respect to the fuel dispenser 10 or by receiving 
information from the transponder indicative of transponder movement. In 
the latter case, the electronics associated therewith, will determine 
whether or not the transponder is moving. For example, the vehicle 
transponder 202 may be operatively associated with the control system of 
the vehicle 200, and the vehicle may send a signal or data via a signal to 
the transponder when the car is preparing to move. This may be triggered 
if the vehicle is started, placed in gear or actually placed in motion, 
although any technique of sensing movement or imminent movement may be 
used. The controller 20 and the dispenser 10 may read the signal or the 
data thereon and control fuel delivery or any audible warnings or 
announcements accordingly. 
Alternatively, the controller 20 may determine a change in the relative 
proximity of a transponder 102, 202 with respect to the dispenser 10 by 
monitoring changes in characteristics of the transmitted signal, such as 
magnitude or phase. A change in magnitude or phase is highly indicative of 
the transponder moving with respect to the dispenser 10. Such a magnitude 
change may be detected by incorporating automatic gain control circuitry 
in the receiver portion of the interrogator or communication electronics 
46 to determine signal strength. Preferably, the gain control circuitry 
feeds an output indicative of signal strength to an analog to digital 
converter to turn the analog signal into a digital string. Changes in the 
string value are indicative of movement. Preferably, each dispenser will 
include or be associated with one or more dispenser antennas 52. However, 
any type of receiver or antenna, including the store antennas 54 and area 
antennas 56 may receive signals from the particular transponder and 
measure such characteristics to determine relative movement, since in 
certain applications, any movement of the transponder may be cause for 
alarm. 
As another alternative, the controller 20 and the associated communication 
electronics 46 may cooperate with a transponder 102, 202 to determine a 
specific location of the transponder in the fueling environment or with 
respect to a fuel dispenser 10. Generally, two or more antennas, such as 
the dispenser antennas 52, store antennas 54, area antennas 56 or any 
combination thereof, may be used to determine the exact or relative 
location of a transponder in the fueling environment. For example, the 
signals received at the various antennas or receivers transmitted from a 
single transponder may be analyzed to compute a location. For example, the 
phase difference of the signal received at the various antennas 52, 54, 56 
will provide information sufficient to determine location. Those skilled 
in the art will quickly recognize the numerous techniques for determining 
location with one, two or more antennas or receivers. Furthermore, the 
communication electronics 46 may be adapted to receive signals from the 
transponder or other source indicative of a vehicle location provided by a 
regional or global positioning system via satellite 60. 
In several aspects of the present invention, it is desirable to determine 
the location and/or proximity of a transponder, whether vehicle mounted or 
carried by a customer, with respect to a specific fueling position of a 
dispenser or interrogation system. In other aspects, it is desirable to 
track the transponder throughout the fueling environment. Although the 
embodiments described herein use the dispenser as a reference, any of the 
interrogation systems in the fueling environment may be adapted to 
determine transponder location and/or proximity. 
Determining location and proximity of a transponder with respect to a fuel 
dispenser in a fueling environment presents a unique problem because the 
fueling environment includes multiple dispensers with multiple positions. 
At any given time, numerous transponders will be in or moving about the 
fueling environment and the many interrogation fields associated with the 
various interrogators. The dispensers and associated control systems must 
distinguish between personal and vehicle-mounted transponders used to 
carry out a transaction from transponders attached to a vehicle driving by 
the fueling position or carried by a person walking by the dispenser. 
Fueling environments must be able to avoid communicating with a second 
transponder during a transaction with a first transponder. 
Texas Instruments has made an attempt at implementing a system in a fueling 
environment capable of communicating with transponders. The beta sites for 
the Texas Instruments system are believed to communicate with transponders 
using an interrogator transmitting an interrogation signal having a 134 
kHz carrier. Any transponders within range of the 134 kHz signal will 
transmit a signal back to the interrogator using a 903 MHz carrier. The 
Texas Instruments system includes a very large loop antenna associated 
with the dispenser for transmitting the 134 kHz signal and a much smaller 
antenna for receiving the 903 MHz signal from the transponder. The 134 kHz 
transmission signal from the interrogator has a very limited communication 
range, which requires the transponder to be within 2-6 inches of the large 
loop antenna to provide the transponder sufficient energy to transmit 
information back to the interrogator. Additionally, the 903 MHz signal 
transmitted from the transponder to the interrogator is substantially 
non-directional and can be heard throughout the entire fueling environment 
and most likely for quite some distance outside the fueling environment. 
Transponder transmissions carrying throughout the fueling environment add 
significant difficulty in correlating a transponder with the proper 
dispenser and respective fueling position. 
In addition to the inherent difficulties in locating and distinguishing 
between transponders within the fueling environment, the Texas Instruments 
system requires different types of antennas, modulation schemes and 
communication electronics for transmitting and receiving signals to and 
from the transponders. Given the limited operating field provided by the 
134 kHz loop antenna, it may be difficult to communicate with 
vehicle-mounted transponders, which necessarily should never be within 2-6 
inches of the fuel dispenser. 
Applicant's invention provides a solution to the difficulties of locating 
and communicating with transponders within the fueling environment by (1) 
providing a communications system operating at frequency ranges which are 
very directional, (2) controlling the power at which the communications 
system operates and (3) simplifying the communications electronics by 
operating at the same carrier frequencies communicating with the 
transponder. Communicating at substantially the same carrier frequency 
allows interrogators to use the same or similar antennas to transmit and 
receive. Furthermore, these more directional frequencies require smaller 
antennas, which are easily integrated into the fueling environment or 
dispenser in an economical and aesthetically acceptable manner. 
The preferred arrangement of applicant's antennas is shown in FIGS. 5 and 
6. In FIG. 5, a side view of a fuel dispenser 10 under an awning 249 is 
shown with multiple configurations of antennas adapted to communicate with 
various transponders proximate to either of the fueling positions A or B. 
The antennas are adapted to transmit, receive or transmit and receive at 
substantially directional frequencies, including those in the microwave 
range, and preferably around about 2.45 GHz. In these embodiments, there 
are basically three suggested antenna locations wherein various 
combinations of antennas at these locations are used. Please note that the 
antennas of FIGS. 5 and 6 are not referenced as 108, for the sake of 
clarity in describing antenna placement. 
The first antenna location is near the middle of a front face of the 
dispenser 10. A mid-dispenser transmit antenna 251 and mid-dispenser 
receive antenna 253 are placed near this midpoint. The antennas may be 
located in the central portion of the dispenser or located anywhere along 
the front face of the dispenser, including near the respective sides of 
the dispenser as shown in FIG. 6. The mid-dispenser antennas 251, 253 
preferably provide a limited power and limited range field pattern to 
communicate with a transponder 102 carried by a customer. The field 
provided by the mid-dispenser transmit antenna 251 is preferably large 
enough to properly communicate with the customercarried transponder 102 in 
the fueling position and in front of the dispenser without requiring the 
customer to remove the transponder from a purse, wallet or pocket and wave 
the transponder next to the dispenser 10 or a receiving antenna. 
Additionally, a top-mount transmit antenna 255 and top-mount receive 
antenna 257 may be provided at or near the top of the dispenser 10 and 
adapted to provide a focused, directional and preferably conically shaped 
field downward over the respective fueling position. These top-mount 
antennas 255, 257 are preferably located on each side of the dispenser 10 
as shown in FIG. 6 in similar fashion to the preferred placement of the 
mid-dispenser antennas 251, 253. The duplication and spacing of these 
antennas help avoid interference caused by people or other objects 
breaking the communication path between the respective antenna and 
transponder. This allows the transponder to communicate with the dispenser 
through one antenna or set of antennas, even if something blocks the field 
from the other set of antennas. 
Another option is to place the antenna substantially directly over the 
fueling position A or B. In such an embodiment, overhead receive antenna 
259 and overhead transmit antenna 261 are mounted over the fueling 
position A, B using an overhead antenna mount 263. The overhead antennas 
261, 263 operate in the same manner as the top-mount antennas 255, 257, 
and may also be spaced apart to provide varying positions to create an 
interrogation field. Notably, the antennas for receiving and transmitting 
may be combined into one wherein a suitable circulator or like electronics 
241 is incorporated into the interrogator or communications electronics to 
provide for reception and transmission from a single antenna. With any of 
these embodiments, the antennas may cooperate directly with the central 
controller 34 and/or with the dispenser controller 20 to allow overall 
system monitoring of transponders at the various positions. In these 
situations, the selected control system will alert the dispenser of 
transponder presence. 
As noted, various combinations of these antennas can be used. For example, 
one embodiment includes two mid-dispenser transmit antennas 251, two 
top-mount transmit antennas 255, and two top-mount receive antennas 257. 
The top-mount receive antennas 257 are adapted to receive signals 
transmitted from the transponder in response to signals from either the 
mid-dispenser transmit antennas 251 or the top-mount transmit antennas 
255. In operation, when a customer-carried transponder 102 enters the 
field provided by the mid-dispenser transmit antenna 251, the transmitter 
reflects a signal which is received by the top-mount receive antenna 257. 
Alternatively, vehicle-mounted transponders 202 may enter the 
interrogation field provided by the top-mount transmit antenna 255 and 
respond with a signal received by the top-mount receive antenna 257. 
The interrogation fields provided by any of the transmit antennas 251, 255, 
259 may be adjusted to control the size and shape of the respective 
fields. For example, the system may be configured to more easily 
distinguish between transponders carried by a person and vehicle-mounted 
transponders by configuring the respective interrogation fields provided 
by the mid-dispenser transmit antenna 251 and the top-mount transmit 
antenna 255 or overhead transmit antenna 259, such that the respective 
interrogation fields do not overlap or overlap in a desired and select 
pattern. Thus, communications resulting from an interrogation with the 
mid-dispenser transmit antenna 251 indicate a transponder carried by the 
customer while communications resulting from the top-mount or overhead 
transmit antenna 255, 259 may be indicative of vehicle-mounted 
transponders. 
Attention is now drawn to FIGS. 7 and 8, which depict a flow chart of a 
basic process for monitoring the location and position of a particular 
type of transponder using top-mount transmit antennas 255 or overhead 
transmit antennas 259 and a mid-dispenser transmit antenna 251 in 
conjunction with one or more top-mount or overhead-mount receive antennas 
257, 261. In this preferred embodiment, one or more of the transmit 
antennas mounted substantially above the customer will alternate sending 
interrogation signals with one or more of the mid-dispenser transmit 
antennas 251. A response to either of these interrogation signals is 
received at a receive antenna mounted substantially above the customer, 
such as one of the top-mount receive antennas 257 or overhead receive 
antennas 261. 
The basic operation of this embodiment begins (block 400) by alternately 
transmitting from the top and mid-mount antennas (block 402). The central 
control system 34 or dispenser control system 20 will monitor for 
responses from transponders within one of the interrogation fields (block 
404). The control system will continue to monitor for a transponder 
response until a signal from a transponder is received (block 406). The 
control system will next determine from which transmission field the 
transponder is responding (block 408). In this embodiment, where the 
transmission fields alternate, the control system will simply determine if 
a transponder response was received during a time period when the top or 
overhead-mount antennas were generating the interrogation field or if the 
response occurred during the time the mid-dispenser transmit antenna 251 
was generating the interrogation field. 
Once the control system determines the field in which the transponder is 
responding, the appropriate location of the transponder is known (block 
410). Typically, the transponder's response to the interrogation signal 
provides transponder identification indicia indicative of the type of 
transponder being interrogated (block 412). The type of transponder is 
generally vehicle mounted or carried by the person. Determining whether 
the transponder is vehicle mounted or carried by the person enables the 
control system to determine how to react to the presence of other 
transponders passing through the various interrogation fields during a 
communication with another transponder or make sure a transponder is 
properly located for the desired transaction. If the control system 
determines the transponder is one carried by a person (block 414) and that 
the transponder was within the mid-antenna field (block 416), the control 
system allows the transaction to continue (block 420). If the transponder 
is a customer-carried transponder that is not within the mid-antenna field 
(blocks 414 and 416), the control system will return to the beginning of 
the process (block 418). The latter situation is indicative of a 
transponder carried by the person being interrogated in one of the top or 
overhead antenna fields, which are preferably used to interrogate 
vehicle-mounted transponders exclusively. Thus, the system preferably 
ignores transponders carried by the person outside of the mid-antenna 
field, which is preferably focused in a manner requiring the customer to 
be substantially in front of the customer interface of the appropriate 
fueling position. The field associated with the mid-dispenser transmit 
antenna 251 is limited only by design choice and may extend several or 
more feet in front and to the sides of the fuel dispenser. 
If the control system is communicating with a customer-carried transponder 
within the mid-antenna field, the control system may monitor for the 
continued presence of the transponder in the mid-antenna field (block 422) 
or allow movement of the customercarried transponder throughout the 
fueling environment (block 422). Notably, it is often desirable to only 
require the customer-carried transponder to be within the mid-antenna 
field long enough to start the transaction and fueling operation, and 
allow the customer to leave the fueling area during the fueling operation. 
Unlike a customer-carried transponder, the control system would preferably 
require the presence of the vehicle in the appropriate transmission field 
throughout the fueling operation for safety reasons. Regardless of how the 
control system monitors the presence or movement of the customer-carried 
transponder during the transaction, the transaction will continue until 
complete (block 426), wherein the process will begin anew (block 428). 
If the control system determines a vehicle-mounted transponder is within 
the appropriate transmission field (block 414), the transaction will 
continue (block 430). Preferably, the control system will make sure that 
the vehicle has stopped moving and has been in position long enough to 
indicate a transaction associated with the responding transponder is 
likely. As noted above, the control system will preferably continue to 
monitor for the vehicle-mounted transponder's presence (block 432) 
throughout fueling. The control system is preferably capable of 
distinguishing responses from the vehicle-mounted transponder associated 
with the transaction from other personal or vehicle-mounted transponders 
entering one or more of the transmission fields (block 434). If a response 
to an interrogation signal is received that does not correspond to the 
vehicle-mounted transponder associated with the transaction, the response 
is ignored (block 436). 
The control system may ignore all responses of customer-carried 
transponders in the top-mount or overhead transmission fields. Erroneous 
responses from other vehicles are rejected based on the control system 
recognizing a response from a vehicle-mounted transponder having a 
different identification indicia from the vehicle-mounted transponder 
associated with the ongoing transaction. Likewise, the control system will 
ignore responses from transponders other than the authorized transponders 
to avoid communicating with transponders of other customers entering the 
field during a transaction. In such case, the control system may check the 
identification indicia to ensure communication continue with the 
appropriate transponder. During this time, the control system will 
continue with the transaction (block 438) until the transaction is 
completed (block 440). 
If the transaction is not complete, the control system will continue to 
monitor for the presence of the vehicle-mounted transponder and any other 
transponders in the area (blocks 432-440). Once the transaction is 
complete (block 440), the process returns to the beginning (block 442). 
Although the preferred embodiment provides for mid and overhead 
transmission fields wherein transponder responses are received near the 
top or above the dispenser, those skilled in the art will recognize that 
numerous modifications of this configuration are within the inventive 
concept disclosed herein and subject to the claims that follow. 
As noted, the interrogation communications system preferably communicates 
using substantially directional radio frequencies in conjunction with 
antennas configured to provide precisely shaped and directed interrogation 
fields. Communications at these frequencies are generally limited to 
line-of-sight communications wherein arranging the antennas to cover a 
common interrogation field from different locations avoids parallax and 
the effect of interference from objects coming between the transponder and 
one of the antennas. Generally, communications will require the absence of 
metal objects coming between the antennas and transponders. Thus, when 
antennas are mounted within the dispenser, glass or plastic dispenser 
walls are preferable. Furthermore, vehicle-mounted transponders are 
preferably placed on the windows or behind non-metal portions of the 
vehicle to avoid interference. 
High-gain antennas may be used to provide a highly directional and 
configurable cone shape covering an area most likely to include a 
transponder when a vehicle is properly positioned for fueling. The antenna 
range and transmission power is typically adjusted to provide the desired 
interrogation field while minimizing the potential for the transponder to 
reflect signals to antennas associated with other fueling positions. 
Another benefit provided by an embodiment of the present invention is that 
spread-spectrum communications limits the likelihood that an interrogator 
in the system will synchronize with a transponder being interrogated by 
another interrogator. Thus, a preferred embodiment of the present 
invention provides for a communications system capable of distinguishing 
between transponder types, limiting the potential of transponders 
erroneously communicating with another interrogator, simplifying 
communications by using the same carrier for transmission and reception, 
extending the interrogation field to more easily communicate with 
vehicle-mounted transponders, reducing the size of the antennas required 
for communication, and allowing either the same or same type of antenna to 
be used for transmission and reception. 
Additionally, the controller 20 may monitor for the presence of both a 
personal transponder 102 and a vehicle or transponder 202 prior to 
beginning fueling operation in order to validate either the personal or 
vehicular transponder, based on the presence of a transponder of the other 
type. Similarly, transponders of the same type may validate each other in 
like manner. Either of these embodiments may be especially useful in fleet 
fueling or like applications. In such applications, one or more 
transponders may be issued to each vehicle and be associated with a 
personal transponder carried by an authorized vehicle operator. Fueling 
may be controlled based on the presence of all associated transponders, 
both vehicular and personal. Once detected, the personal transponder may 
move about the fueling environment, while any movement at the one or more 
vehicle transponders may result in awaiting and/or halting fuel delivery. 
Certain modifications and improvements will occur to those skilled in the 
art upon reading the foregoing description. It should be understood that 
all such modifications and improvements have been deleted herein for the 
sake of conciseness and readability, but are properly within the scope of 
the following claims.