U.S. patent number 3,731,277 [Application Number 05/049,235] was granted by the patent office on 1973-05-01 for data accumulation and transmission system for use between remote locations and a central location.
This patent grant is currently assigned to Gulf Research & Development Company. Invention is credited to Ronald L. Krutz, Thomas J. Villella.
United States Patent |
3,731,277 |
Krutz , et al. |
May 1, 1973 |
DATA ACCUMULATION AND TRANSMISSION SYSTEM FOR USE BETWEEN REMOTE
LOCATIONS AND A CENTRAL LOCATION
Abstract
A data accumulation and transmission system wherein a plurality
of independent data generators are sequentially triggered in such a
manner that the rate of speed of the triggering pulse is much
greater than the rate of speed of data production. Double counting
is prevented by utilizing the trailing edge of each data pulse to
reset the device which the triggering pulse sets. The data is
communicated, for example, across a telephonic connection in a
highly reliable manner by utilizing a clock to drive the data out
of a shift register and to simultaneously gate-in the clock pulses
with the data at the sending telephone.
Inventors: |
Krutz; Ronald L. (New
Kensington, PA), Villella; Thomas J. (New Kensington,
PA) |
Assignee: |
Gulf Research & Development
Company (Pittsburgh, PA)
|
Family
ID: |
21958754 |
Appl.
No.: |
05/049,235 |
Filed: |
June 24, 1970 |
Current U.S.
Class: |
340/870.03 |
Current CPC
Class: |
B67D
7/228 (20130101); H04M 11/002 (20130101) |
Current International
Class: |
B67D
5/22 (20060101); H04M 11/00 (20060101); H04q
003/00 () |
Field of
Search: |
;340/151R,163R,147R,147LP |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pitts; Harold I.
Claims
We claim:
1. A method for accumulating data pulses produced by a plurality of
data pulse generators, wherein each data pulse generator is capable
of producing a stream of data pulses independently of all of the
other data pulse generators of said plurality, comprising the steps
of supplying each data pulse of each stream of data pulse from each
data pulse generator to a separate data pulse passing means,
sequentially supplying a triggering pulse to each of the data pulse
passing means at a frequency greater than the maximum frequency of
data pulse generation by each of said data pulse generators,
causing each data pulse passing means to produce an output when
said data pulse passing means simultaneously senses a data pulse
and a triggering pulse on its input side, and causing said data
pulse passing means to be insensitive to additional triggering
pulses to produce an additional output after it has so
simultaneously sensed a data pulse and a triggering pulse until
after said data pulse passing means has sensed the falling edge of
said last mentioned data pulse, thereafter causing said data pulse
passing means to be ready to produce another output upon the
simultaneous presence of another data pulse and another triggering
pulse at its input side after it has sensed said falling edge of
said last mentioned data pulse, whereby said data pulse passing
means produces only one output for each data pulse regardless of
any additional triggering pulse supplied to said data pulse passing
means while each data pulse is present at the input side of said
data pulse passing means.
2. The method of claim 1, and filtering each data pulse from a data
pulse generator before it is passed to its associated data pulse
passing means.
3. The method of claim 1, wherein said triggering pulses are
produced by decimal counting means, and said sequential operation
is achieved by directing triggering pulses from successive decimal
numeral locations on said counting means to each of said data pulse
passing means sequentially.
4. The method of claim 1, wherein said data pulse generators
comprising a plurality of retail gasoline dispensing pumps, and
each of said pumps includes transducer means for transforming the
flow of gasoline therethrough into said steam of data pulses.
5. The method of claim 1, each of said data pulse passing means
comprising a bistable multivibrator.
6. A method of communicating a data count from a first location
across communication means having at least two channels to a second
location, comprising the steps of causing the data count to be
present on a shift register at said first location, producing a
continuous stream of control pulses at a predetermined frequency,
and simultaneously supplying said stream of control pulses to said
shift register and to the portion of said communication means at
said first location to simultaneously transmit each data bit from
said shift register across one of said at least two channels of
said communication means together with a control pulse across
another of said at least two channels of said communication means
to said second location.
7. The method of claim 6, wherein aid communication means comprises
a telephonic connection between said first and second locations,
wherein each data bit is simultaneously transmitted across said
communication means together with a control pulse by causing each
control pulse by itself to activate the coil of a first relay of a
pair of relays, and to simultaneously activate the coil of the
second of said pair of relays only if a "high" data bit from said
shift register is also present at the input of the coil of said
second relay.
8. The method of claim 6, additionally comprising the step of
supplying a number on said shift register in addition to the data
count thereon to identify said first location to said second
location.
9. The method of claim 6, wherein said data count is made up of the
data counts on a plurality of independent data counters, and
wherein said shift register is large enough to simultaneously
follow the data counts on all of said plurality of data counters,
whereby the data is supplied to said shift register from said
counters independently and in parallel and is moved out of said
shift register all together and sequentially.
10. A circuit for accumulating data pulses produced by a plurality
of data pulse generators, each of said data pulse generators being
operable to produce a stream of data pulses independently of all of
the other data pulse generators of said plurality, said circuit
comprising a data pulse passing means connected to each of said
data pulse generators, said circuit comprising timing means which
includes clock means for producing a continuous stream of timing
pulses at a predetermined frequency, said timing means comprising
triggering means driven by said timing pulses for sequentially
directing a triggering pulse to each of said data pulse passing
means, wherein said predetermined frequency of timing pulse
production by said clock means divided by the number of said data
pulse generators is greater than the maximum frequency of data
pulse generation by each of said data pulse generators; each of
said data pulse passing means being of such a nature that it
produces an output upon simultaneously sensing a data pulse and a
triggering pulse on its input side, that is is insensitive to
additional triggering pulses to produce additional outputs after it
has so simultaneously sensed a data pulse and a triggering pulse
until after it has sensed the falling edge of said last mentioned
data pulse, and that it will be rendered ready to produce another
output after it has so sensed the falling edge of said last
mentioned data pulse and upon the simultaneous presence thereafter
of another data pulse and another triggering pulse; whereby, said
data pulse passing means produces only one output for each data
pulse regardless of any additional triggering pulse supplied to
said data pulse passing means while each data pulse is present at
the input side of said data pulse passing means, and said circuit
further comprising means for counting all of the data pulses
passing all of said data pulse passing means.
11. The method of claim 10, said clock means including means to
produce said timing pulses at different predetermined
frequencies.
12. The combination of claim 10, said circuit, with the exclusion
of said data pulse generators, comprising solely solid-state
electronic components.
13. The combination of claim 10, said data pulse generators
comprising a plurality of retail gasoline dispensing pumps, and
each of said pumps including transducer means for transforming the
flow of gasoline therethrough into said stream of data pulses.
14. The combination of claim 10, each of said data pulse passing
means comprising a bistable multivibrator.
15. The combination of claim 14, said circuit comprising a filter
interposed between each of said data pulse generators and its
associated bistable multivibrator.
16. The combination of claim 10, said triggering means comprising
decimal counter means for counting the timing pulses produced by
said clock means, said decimal counter sequentially operating each
of said data pulses passing means by directing triggering pulses
from successive decimal numeral locations thereon to each of said
data pulse passing means sequentially.
17. The combination of claim 16, said decimal counter means
comprising a BCD counter having its input side connected to said
clock means and a one-of-ten decoder having its input side
connected to the output side of said BCD counter.
18. The combination of claim 10, data pulse counting means
including data pulse conditioning means which comprises a oneshot
multivibrator.
19. The combination of claim 10, said data pulse counting means
including data pulse accumulating means which comprises an "or"
gate having its input side operatively cooperable with the outputs
of all of the data pulse passing means.
20. The combination of claim 10, said data pulse counting means
comprising a multi-stage BCD counter operatively cooperable with
the output sides of all of said data pulse passing means.
21. The combination of claim 10, said data pulse counting means
comprising a one-shot multivibrator connected to the output of each
of said data pulse passing means, an "or" gate having its input
connected to the outputs of all of said one-shot multivibrators,
and a multi-stage BCD counter connected to the output of said "or"
gate.
22. A system for communicating a data count present on a shift
register at a first location across communication means having at
least two channels to data receiving means at a second location
which is remote from the first location, switch means at said
second location for transmitting a transmit command from said
second location to said first location across said communication
means, clock means at said first location for producing a
continuous stream of control pulses at a predetermined frequency,
and said first location comprising circuit means for simultaneously
supplying said control pulses to both said shift register and said
communication means and for interconnecting said shift register and
said communication means to simultaneously transmit each bit of
data in said shift register across one channel of said
communication means and one control pulse across another channel of
said communication means to said second location.
23. The combination of claim 22, said circuit means comprising an
array of a pair of relays and an "and" gate associated with the
coil of each of said relays, each of said relays comprising a pair
of normally open contacts connected to said communication means in
such a manner that closing of said contacts causes a pulse to be
transmitted across a separate channel of said communication means,
each of said "and" gates having a pair of inputs, one of the inputs
of each of said "and" gates comprising said continuous stream of
control pulses, the second input of one of said "and" gates
comprising a steady signal, the other of said inputs of the "and"
gates comprising the output of said shift register, circuit means
interconnecting the output of each of said "and" gates with the
coil of a respective one of said relays in such a manner as to
close the contacts of each of said relays when each of said "and"
gates produces an output pulse, whereby one of said channels of
said communication means will transmit one pulse for each control
pulse and the other of said channels will simultaneously transmit a
pulse only when a high data bit pulse is present at the output of
said shift register, and whereby said stream of control pulses also
controls the progression of the data bits in said shift register
corresponding to the data count on said shift register out of said
shift register.
24. The combination of claim 22, said communication means
comprising a telephonic connection between said first and second
locations.
25. The combination of claim 22, and said shift register further
comprising manually controllable means for permitting creation of
an additional number on said shift register in addition to the
numbers corresponding to said data count, whereby said additional
number may be used for purposes of identifying said first location
to said second location.
26. The combination of claim 22, said data receiving means
comprising a second shift register and means to display the data
count received thereon from said first location.
27. The combination of claim 26, said data receiving means further
comprising a computer, and means interconnecting said computer and
said switch means for causing automatic operation of said switch
means.
28. The combination of claim 22, wherein said data count is made up
of the data counts on a plurality of independent data counters, and
wherein said shift register is large enough to simultaneously
follow the data counts on all of said plurality of data counters,
whereby the data is supplied to said shift register from said
counters independently and in parallel and is moved out of said
shift register all together and sequentially.
29. A system for accumulating data pulses produced by a plurality
of data generators and for communicating the accumulated data count
from a first location across communication means to a second
location remote from said first location, each of said data pulse
generators being operable to produce a stream of data pulses
independently of all of the other data pulse generators of said
plurality, a data pulse passing means connected to each of said
data pulse generators, timing means including clock means for
producing a continuous stream of timing pulses at a predetermined
frequency, said timing means comprising triggering means for
sequentially directing a triggering pulse to each of said data
pulse passing means, wherein said predetermined frequency of timing
pulse production by said clock means divided by the number of said
data pulse generators is greater than the maximum frequency of data
pulse generation by each of said data pulse generators, each of
said data pulse passing means being of such a nature that it is
rendered operative to pass a data pulse from its associated data
pulse generator therethrough and onto subsequent portions of the
system upon receipt of a triggering pulse and of such a nature that
is rendered inoperative to so pass a data pulse upon passage
therethrough of a selected portion of each data pulse, circuit
means for directing all of the data pulses passing all of said data
pulse passing means to a shift register to thereby create a data
count on said shift register, said shift register being located at
said first location, data receiving means at said second location,
switch means at said second location for transmitting a transmit
command from said second location to said first location across
said communication means, said first location comprising said
circuit means for supplying said continuous stream of timing pulses
to both said shift register and said communication means
simultaneously and for interconnecting said shift register and said
communication means, whereby said communication means
simultaneously transmits each data bit in said shift register
together with one timing pulse to said second location.
30. The combination of claim 29, frequency divider means at said
first location for changing the predetermined frequency of the
timing pulses supplied to said shift register and said
communication means, whereby the timing of the data accumulation
may be different from the timing of the data transmission.
31. The combination of claim 29, said data pulse generators
comprising a plurality of retail gasoline dispensing pumps, and
each of said pumps including transducer means for transforming the
flow of gasoline therethrough into said stream of data pulses.
32. The combination of claim 29, each of said data pulse passing
means comprising a bistable multivibrator.
33. The combination of claim 32, said circuit comprising a filter
interposed between each of said data pulse generators and its
associated bistable multivibrator.
34. The combination of claim 29, said triggering means comprising
decimal counter means for counting the timing pulses produced by
said clock means, said decimal counter sequentially operating each
of said data pulses passing means by directing triggering pulses
from successive decimal numeral locations thereon to each of said
data pulse passing means sequentially.
35. The combination of claim 29, and data pulse counting means,
said data pulse counting means comprising a one-shot multivibrator
connected to the output of each of said data pulse passing means,
an "or" gate having its input connected to the outputs of all of
said one-shot multivibrators, and a multi-stage BCD counter
connected to the output of said "or" gate.
36. The combination of claim 29, said circuit means comprising an
array of a pair of relays and an "and" gate associated with the
coil of each of said relays, each of said relays comprising a pair
of normally open contacts connected to said communication means in
such a manner that closing of said contacts causes a pulse to be
transmitted across a separate channel of said communication means,
each of said "and" gates having a pair of inputs, one of the inputs
of each of said "and" gates comprising said continuous stream of
control pulses, the second input of one of said "and" gates
comprising a steady signal, the other of said inputs of the "and"
gates comprising the output of said shift register, circuit means
interconnecting the output of each of said "and" gates with the
coil of a respective one of said relays in such a manner as to
close the contacts of each of said relays when each of said "and"
gates produces an output pulse, whereby one of said channels of
said communication means will transmit one pulse for each control
pulse and the other of said channels will simultaneously transmit a
pulse only when a high data bit pulse is present at the output of
said shift register, and whereby said stream of control pulses also
controls the progression of the data bits in said shift register
corresponding to the data count on said shift register out of said
shift register.
37. The combination of claim 29, said communication means
comprising a telephonic connection between said first and second
locations.
38. The combination of claim 29, and said shift register further
comprising manually controllable means for permitting creation of
an additional number on said shift register in addition to the
numbers corresponding to said data count, whereby said additional
number may be used for purposes of identifying said first location
to said second location.
39. The combination of claim 29, said data receiving means
comprising a second shift register and means to display the data
count received thereon from said first location.
40. The combination of claim 39, said data receiving means further
comprising a computer, and means interconnecting said computer and
said switch means for causing automatic operation of said switch
means.
41. The combination of claim 29, said plurality of data pulse
generators consisting of a plurality of groups of data pulse
generators, said circuit including a separate and independent data
counter for each group of data pulse generators, wherein said data
count is made up of the data counts of said plurality of
independent data counters, and wherein said shift register is large
enough to simultaneously follow the data counts on all of said
plurality of data counters, whereby the data is supplied to said
shift register from said counters independently and in parallel and
is moved out of said shift register all together and sequentially.
Description
This invention relates to data gathering and transmission systems,
and more in particular pertains to such a system for use between a
plurality of separated locations and a central point, such as a
computer center. The data is generated at each of the separate
locations by a plurality of separate and independent devices or
data generators. The central location, by means of a telephonic
hook-up or other communication means, may interrogate each of the
remote locations to gather the data from all of the data generators
at that location.
As is obvious, such a system is useful in a varied and large number
of different kinds of applications, such as transmission of credit
card sales data, inventory control, credit verification, remote
reading of metering devices generally, and the like. However, the
invention was developed specifically for and will be described
primarily in connection with such a system for use between a data
center connected to a plurality of otherwise conventional retail
gasoline outlets or service stations.
For ease of description, the invention may be thought of as
comprising two portions, which are in fact integrated together, but
which lend themselves to functional separation. These two portions
are a data gathering system having a part in operative cooperation
with each of the pumps in the station or other pulse data
generators, and secondly a data transmission system which includes
commercially available telephonic data transmission equipment, for
example, data transmission equipment as supplied by the Bell
Telephone Companies. Of course, the invention is not limited to any
particular model of such telephonic equipment or even to the
telephone per se, since other means, such as telegraph lines, radio
systems, or the like, could be used, with suitable changes in the
apparatus of the invention. However, as mentioned above, this
division into sections is a matter of convenience only, since, in
fact, a single circuit or "black box" could be provided at each
service station with the data pulses from each pump brought to a
single piece of electronic hardware in the station, or perhaps with
satellite parts thereof at each pump. Thus, each piece of apparatus
at each station would include virtually the entire invention,
namely, the entire data gathering "section" and all of the data
sending part of the data transmission "section". The remainder of
the apparatus of the invention, one piece of equipment to service
all of the remote locations, would comprise merely the remainder of
the data transmission section and some sort of data receiving means
such as a shift register and/or display. This is the form the
prototype apparatus built to test the invention has taken.
The utility of the invention in the gasoline business is manifest,
and includes the capability of automated inventory control,
automated dispatching of tank trucks to the stations, stock loss
control, automated money accounting including service station
billing, remote meter reading, and the like. Further, starting from
the system of the invention as a base, still more sophisticated
uses are possible, such as automated credit card retailing which
would include automatic billing of the customer, checking for
expired or otherwise invalid credit cards, and automated and more
rapid customer billing which is worth substantial monies to a major
oil company by holding customer accounts receivable at a lower
level.
Referring again to the artificial but convenient separation of the
invention into sections above, the data gathering section comprises
a highly versatile circuit adapted for use with virtually any
number of pumps in a conventional service station. In the specific
form of apparatus disclosed below, maximum capacity is ten pumps
for one grade of gasoline, but this number can be increased, almost
without limit, for an exceptionally large station, or in other
applications to which the invention might be applied. More than ten
pumps is somewhat unlikely because each grade of gasoline is
handled separately, and it would be an exceptionally large station
which would have more than ten pumps for one grade.
One problem, overcome by the invention, flows from the fact that
each pump is a completely independent input device, that is, each
pump operates or does not operate without regard to the others,
and, when operating, can operate at an infinity of different
speeds. In the specific apparatus described below, five pumps for
one grade are shown as a more or less arbitrary example of a
typical installation. Each of the five pumps can operate or not
operate without regard to the other four, and each can operate at
many different speeds, although the most typical speed will be top
speed as when the pump is operated under the control of the
automatic shut-off nozzle. Thus, given the above as the environment
of the invention and given that transducer means are provided at
each pump to transform the flow of gasoline into a stream of
electrical pulses proportional to the liquid flow, as will appear
in the detailed description below, then the circuitry must be able
to accommodate, within one station, the possibility of simultaneous
creation of two or more pulses generated by two or more separate
pumps. Further, the circuitry must never lose a pulse and must
never create spurious or additional pulses. This high degree of
reliability is needed for proper inventory control and for proper
financial control.
In overcoming these problems and achieving these goals, the
invention utilizes the fact that each of the random data pulse
generators, each pump, has a known maximum speed. The circuitry
provides a continuously "circulating" triggering pulse which is
used to pass the raw data pulses through intermediate stages of the
circuitry. The speed of this "circulating" triggering or gating
pulse is caused to be much greater than the highest possible speed
of data pulse generation, and this speed relationship is utilized,
as will be described in detail below, to solve the simultaneous
data pulse generation problem as well as to assure correct
accumulation of the data.
The invention solves the potential problem of usage of the pump
creating false pulses by providing means to ground the input end of
the circuit at all times except when the pump motor is
operating.
The data transmission section of the invention is partly located at
the service station and operates in conjunction with the means
utilized to accumulate the data from one of the pumps, with some
communication means such as a data telephone hook-up, and finally
with interrogation means and data receiving means including a
display, a computer, and/or the like, at the central location or
data center. An essential here, again with an eye to one of the
prime pre-requisites of high reliability, is the provision of means
to provide a fiducial, clock, or control pulse which is transmitted
with the data by the communication means from the station to the
data center, and, as will appear below, in the opposite direction
as well, so as to assure that only the data is counted, no data is
lost, and that no spurious or additional pulses are included.
Another problem is accommodating for the nature of the environment,
e.g., the constant presence of automobiles having high voltage
ignition circuits which could severely disrupt the intended
operation of electronic pulse handling circuitry. The invention
corrects for this potential problem by providing suitable noise
depressant means, such as grounding the pump data generator after
each sale, as will appear in detail below, using relatively noise
immune logic components at the input end, and using suitable RC
protecting networks (loss pass filters) between each pump and the
circuit of the invention.
The invention provides means to simplify the process of
interrogation of each station by the central location while at the
same time holding the cost of equipment required at each remote
location to a minimum. Referring again to the artificial division
of the invention into "sections", a unique interface is provided so
that one data sending apparatus at the station can accommodate as
many separate data gathering systems as are present, for example,
each grade of gasoline will require its own data gathering
"section".
The above and other advantages of the invention will be pointed out
or will become evident in the following detailed description and
claims, and in the accompanying drawing also forming a part of the
disclosure, in which:
FIG. 1 is a schematic diagram of one type of environment in which
the invention may be used;
FIG. 2 is an electrical schematic diagram of the data accumulation
section;
FIG. 3 is a detailed view of part of FIG. 2;
FIG. 4 is an electrical schematic diagram of the remainder of the
apparatus of the invention which includes part of the data
transmission section, the communication means, and the apparatus
required at the central location or data center; and
FIG. 5 is a simplified sketch showing the manner of operation of a
part of the apparatus of FIGS. 2 and 4.
Referring in detail to the drawing, in FIG. 1 there is shown a
plurality of remote locations 10, which may be conventional retail
gasoline service stations. A central location 12, which may be a
data center or computer center is joined to each of the stations 10
by separate communication means such as separate telephonic
hook-ups, which communication means are indicated by the lines 14.
Referring to FIG. 2, there is shown part of the installation at
each of the stations 10, and referring to FIG. 4, there is shown
the remainder of each of the installations at each service station
10, the communication means 14, and the entire installation at the
computer center or central location 12.
Referring now in detail to FIG. 2, each service station 10 includes
a separate plurality of gasoline dispensing pumps 16 for each of
the various grades of gasoline. In FIG. 2 there are shown five
pumps 16 for one particular grade, it being understood that there
will be approximately five for each of the other grades sold by
that station, and that the circuitry up to counter 40, as described
below, will be duplicated for such other groups of pumps.
Means are provided within each pump in the station to convert the
flow of gasoline through the pump into a stream of data pulses the
rate of which is proportional to the amount of liquid passing
through the pump. Such pulse generating transducers are
commercially available, or alternatively the apparatus disclosed in
our copending patent application Ser. No. 815,838, filed Apr. 14,
1969, and entitled "Gasoline Pump Computer", now U. S. Pat. No.
3,598,283, assigned to the same assignee as the present invention,
may be advantageously used. A line 18 delivers the raw data pulses
produced by such means in the pump 16 to filter-like means 20 which
serve to suppress noise produced by the proximity of high voltage
automotive ignition systems, and to protect the remainder of the
circuitry. Filter means 20 include a low pass filter such as an RC
network, and a relatively noise immune logic gage, or other
suitable means well known to those skilled in the art. After
filters 20, the "cleaned-up" pulses are present on a pair of lines
22 which feed the pulses to pulse passing means which may be a
bistable multivibrator or flip-flop 24. A signal inverting device
26 is included in one line 22 of each pair. Each pulse is
reproduced and supplied by the lines 22 to the flip-flop 24 as both
a negative-going and as a positive-going pulse, because such pulse
treatment is required by the nature of the flip-flop, as is
known.
Means are provided to assure that no spurious pulses are supplied
to filter means 20 and the remainder of the circuitry because of
the manner of usage of the pumps 16. Virtually all retail gasoline
dispensing pumps in use today have two manual controls; a switch or
push-button which resets the counting mechanism, and a switch which
turns the pump motor on and off. The pump motor switch activator is
usually a relatively heavy piece of metal which includes a flange
or other means to hold the gasoline dispensing nozzle, but only
when the pump switch is in the off position. The pump includes an
interlock between these two controls which prohibits turning on the
pump motor unless the counters are first reset to zero, and which
also prohibits resetting the counting mechanism unless the pump
motor is off.
The potential problem which is overcome by the switch arrangement
of the invention shown in FIG. 3 is that if the circuit is not
grounded while the pump counting mechanism is being reset, then the
circuitry of the invention may "see" the resetting motion of the
counter mechanism as pulses. This potential source of error is
eliminated by the provision of a normally closed switch 15 wired
between line 18 and a suitable ground in the pump and mechanically
or otherwise connected to the manual pump motor control switch. The
addition of such a switch is a simple matter for a skilled
mechanic. Since the pump's own interlock assures that the pump
motor switch must be off in order to reset, thereby placing switch
15 in its normally closed position, the FIG. 3 circuitry assures
that line 18 will be grounded during the act of resetting the
pump's counting mechanism. The second switch 17, wired in parallel
with switch 15, represents that part of the pulse generating
transducer in the pump used to produce the raw data pulses.
Whatever such means 17 are used, they are preferably arranged so
that switch 17 is closed when the pump's counting mechanism is at
the zero position, thus assuring that the circuitry is grounded
after resetting is complete and before the next pumping operation
begins.
Thus, the FIG. 3 circuit assures that raw data pulses will be
produced only during the act of dispensing gasoline.
Referring back to FIG. 2, the flip-flops 24 require a triggering
pulse to permit passage of signals from their input side, the lines
22, across to their output side, lines 28. The required triggering
pulses are separately supplied to each flip-flop on a line 30
running from the timing means described further below. Flip-flop
output line 28 delivers pulses to data pulse conditioning means
which may be a one-shot multivibrator 32, and a line 34 from each
one-shot 32 delivers the pulses to data pulse accumulating means
which may be an "or" gate 36.
Before proceeding deeper into the detailed description of the
circuit, it should be understood that the schematic drawings
forming part of this disclosure have been distilled from
substantially more complex working drawings. Thus, this description
is at least partly in functional terms, leaving much of the detail
to the expertise of the worker skilled in the art. For example, in
the successfully constructed and operating prototype apparatus, the
"lines" 30 are not literally a single electrical conductor but each
is a pair of such conductors, and may be conventional wiring and
internal circuitry of purchased components. Thus, the term "line"
as used herein will be understood to mean one or more electrical
conductors. Similarly, "or" gate 36 is in fact a NAND gate, but it
is functionally equivalent to an "or" gate. Many such
simplifications have been made, but no additional ones will be
pointed out, unless necessary for an understanding of the
functioning of the circuit, since such equipment, its capabilities,
the interchangeability of such components, an such techniques, are
well within the skill of the ordinary worker in the art.
The output signals from "or" gate 36 are fed on a line 38 to
suitable counting means, which may be a multi-stage binary coded
decimal (BCD) counter 40. A counter 40, see FIG. 5, is required for
each grade of gasoline, and all the circuitry of FIG. 2, with the
exception of the timing means, is provided for each different set
of pumps 16. The lines 30 are shown broken to indicate that the
timing means are shared. As will appear in detail in the
"Operation" section below, the essential timing required for
operation of the invention is provided by a device 42 which may be
thought of as a clock in that it continuously produces pulses at a
regular frequency. Such clocks are commercially available with
means to vary the period of the pulses. In any particular
installation, one clock frequency will usually be sufficient, but
the adjustable feature may be desired for more versatility or where
the invention is used in some other environment. The timing pulses
produced by clock 42 at a frequency of T pulses per unit time are
present on a line 44. The pulses on line 44 may be either
positive-going or negative-going, depending upon the required
interaction with the other components used in constructing any
specific apparatus in accordance with the invention. In the
successfully constructed embodiment of the invention these pulses
are positive-going.
As is known, the description "positive-going" or "negative-going"
refers to the nature of the pulse. That is, assuming the pulse is
of square shaped, then in the direction of the progression of time
the first leg of the square either rises from whatever the base
value is being used to some higher positive value (positive-going),
or conversely, falls from the base value to some less positive
value, (negative-going). The concept of zero as a base should be
avoided since the base itself could have a positive or a negative
value.
The clock pulses on line 44 feed the input side of a single stage
BCD counter 48. As is known, and as is explained in detail in our
previous patent referred to above, device 48 is a commercially
available item which counts the pulses received on input line 44
and produces coded pulses on a set of lines 50 representative of
the numbers 0 through 9. Counter 48 has the capacity to count as
high as 15, but it is constrained, by simple alteration, to count
up to 9 only. The coded signals on lines 50 feed the input side of
a decoding device 52, which changes the binary code decimal signals
to true decimal signals supplied on the output lines 30 described
below. Thus, components 48 and 52 operating together may be thought
of as a single decimal counter, and are used for all the sets of
pumps in the station.
The circuitry of FIG. 2, with the exception of the data pulse
generators in the pumps 16, is advantageously all solid-state,
rather than vacuum tube, so as to yield the advantages of lower
power and voltage requirements, smaller size, and rugged, reliable
and relatively inexpensive construction.
As is now evident, each remote location will have a number of
counters 40 equal to the number of different grades of gasoline
sold at that station. Typically, there are three grades. Referring
to FIG. 5, the three counters are indicated as 40-1, 40-2 and 40-3,
and the manner of their connection to the shift register 54 of FIG.
4 is diagrammatically shown. The concept underlying FIG. 5 is that
the three data accumulation circuits, each like FIG. 2, are
interfaced with the single data transmission circuit, FIG. 4, by
providing one shift register 54 large enough to accommodate all the
counters 40. Thus, when the central location interrogates a station
all the data as to all three grades of gasoline will be sent out in
one continuous stream, thereby eliminating the need to make a
separate interrogation in regard to each grade of gasoline. The
data for each grade can be separated at the central location 12 in
a variety of ways, such as by providing means to insert a "dummy"
between the data for each grade, or some symbol other than a number
between grades, or by simply physically separating the three
displays at the data center, the number of digits per grade being
known. Other ways of achieving data separation will be obvious to
those skilled in the art.
Thus, the arrangement of FIG. 5 allows parallel data accumulation
from independent counters, and sequential data transmission of the
composite data count.
Referring now to FIG. 4, there is shown the remainder of the
circuitry at remote location 10, all of the circuitry at the
central location 12, and the telephonic communication means
interconnecting the two locations. The FIGS. 2 and 4 circuitry are
connected together between the counters 40 and a shift register 54.
The connection is indicated by the sets of lines 56 which
interconnect the respective stages of all the counters 40 and shift
register 54. These two components, 40 and 54, are shown broken in
the drawing to indicate that any number of counting stages could be
utilized. The shift register 54, however, will have at least one
more stage 58 than the sum of all the stages of counters 40. The
additional stage 58 comprises means to manually set a number
thereon, not shown, which number will identify the particular
station 10, the first location, to the data center 12, the second
or central location. If required, of course, the extra stage 58
could comprise more than one stage, dependent upon the number of
remote locations being serviced. The shift register may require two
or more additional stages to accommodate the intradata "dummies,"
symbols, or the like, if such are used.
The showing of a shift register is exemplitive only, and, as will
appear more clearly in the Operation section below, the term shall
be understood to include any sort of device in which data is stored
and moved in a sequential fashion, rather than along parallel lines
or in any other manner. As is now clear, the two "artificial"
portions of the invention, the circuitry of FIGS. 2 and 4 is
artificial in the sense that in the intended use of the invention
they are integrated together. The two sections have separate
utility. For example, the FIG. 2 circuitry could end at the counter
40, with perhaps the addition of some display means, where it is
desired to only accumulate the total count of the data pulse
generators at a single location and not to transmit the data to
some other location. Similarly, the data transmission means of FIG.
4 can be used in any environment where it is desired to transmit a
data count from a shift register at one location to some data
receiving means at some other location, where the two locations are
physically separated from each other but connected together by some
communication means.
As is known, each set of lines in the sets 56 consists of four
lines, as four is the number of signals needed to represent any
single digit number in the BCD code.
The timing of the operation of several components in the FIG. 4
circuitry is critical, and all of these portions are connected to a
single timing or control source, which may comprise the clock 42 of
FIG. 2. Referring to FIG. 4, a tap from line 44 feeds a frequency
divider circuit 60, which circuit may be any one of a wide variety
of such commercially available items. The output of divider 60 is
present on a line 62, and comprises a chain of control or timing
pulses having a frequency t. Suitable frequency divider circuits
are commercially available, or may be easily built according to
circuits found in handbooks. For example, Motorola Integrated
Circuit Data Book, Aug. 1968. Line 62 feeds various parts of the
FIG. 4 circuitry, as described below.
Communication means 14 will advantageously comprise equipment
intended to work in conjunction with the commercial telephone
network. In the form of the invention constructed to date, a Bell
Telephone Company 401 H data transmitter and 401 J data receiver
were used. These instruments have a number of connecting points or
terminals on each side to which the user may attach whatever
equipment he desires so long as his equipment will perform the
function required by the special telephone at those terminals.
Referring to the right side of FIG. 4, which corresponds to the
data center, a pair of lines 64 and 66 connect the appropriate
terminals on the data center special telephone 14a to a switching
device 68. Device 68 is not supplied by the telephone company. A
switching member 70 on device 68, in conjunction with data set 14a,
renders the data set in condition to transmit and receive either
data or normal voice.
The overall manner of using data set 14a and the sending data set
14b at the remote location is first to send a signal from the data
center to the station which may be thought of as the "transmit
command." This command signal enables the transmitting station, or
remote location, to begin sending data. When the data center's
telephone must be rendered into a different configuration in order
to receive the data, and a corresponding change of configuration
must take place at the sending location. The above sequence of
events is a result of the fact that the particular telephones used
are capable of unidirectional transmission only. The telephone
company and others do have equipment available which can transmit
data in both directions simultaneously, but such equipment is
considerably more expensive, to either purchase or rent, than the
simpler equipment around which this portion of the invention has
been built. The simpler, less expensive equipment was used because
no substantial loss of speed is suffered, and substantial economies
are realized.
In addition to the lines 64 and 66 described above, six additional
contacts on receiving equipment 14a are utilized and these are
connected to lines 72, 74, 76, 78, 80 and 82 respectively. There
are other terminals on the particular equipment 14a used to provide
a second channel, but a second channel is not utilized in the
invention and therefore is not shown. The lines 72 and 74 connect
to the opposite sides of a pair of normally closed contacts 86 on a
relay 84. When contacts 86 are closed, receiver 14a is in condition
to receive data, and when the contacts 86 are open, equipment 14a
is in condition to send the transmit command to the data sending
equipment 14b. The coil 88 of relay 84 is connected by a line 90 to
the Q terminal of a one-shot multivibrator 92.
The next pair of lines 76 and 78 are used to send the transmit
command, and these lines run to the opposite sides of the normally
open contacts 96 of a relay 94, the coil 98 of which is connected
by a line 100 to the Q terminal of one-shot 92. As mentioned above,
the schematic of FIG. 4 is simplified, and certain parts, such as
current amplifiers or buffers in the lines 90 and 100 and suitable
diodes or other suitable protection means for the coils 88 and 98
have been omitted.
The remaining two lines 80 and 82 are used to receive data and
gated clock or control pulses from the remote location 10 via the
communication means 14. These lines terminate at a receiving shift
register 102. An extension of line 90 extends to the reset terminal
on shift register 102. A cable 104 interconnects shift register 102
with means 106 which may comprise a data display device, and/or a
suitable computer for handling the data received. In the event
means 106 includes a computer, this machine may be used to
automatically and cyclically interrogate all of the remote
locations and to operate the data receiving means and circuitry on
the right hand side of FIG. 4. Thus, the term "data receiving
means" as used herein shall be understood to denote means such as a
shift register, a data display device, and/or a computer, and the
like.
Completing the right hand side of FIG. 4 there is provided switch
means such as a manually or mechanically operated switch 108, the
normally open terminal of which is connected by a line 110 to the
set (S) terminal of a flip-flop 112, and the normally closed
terminal of which is connected by a line 114 to the reset (R)
terminal of flip-flop 112. A line 116 interconnects the output of
the flip-flop 112 and the input of one-shot 92.
Referring to the left side of FIG. 4, the transmitting data set
comprises seven lines, 118, 120, 122, 124, 126, 128 and 130. Lines
126, 128 and 130 service the contacts on a pair of relays 132 and
134. Relay 132 comprises a pair of normally open contacts 136 and a
coil 138, and relay 134 comprises a pair of normally open contacts
140 and a coil 142. Line 128, known as the "phone-common", is
connected to one side of each of the contacts 136 and 140. Line 126
connects to the other side of contacts 136 and line 130 connects to
the other side of contacts 140. One side of coil 138 is suitably
grounded, and the other side of said coil is connected to a line
144 which connects to the output side of an "and" gate 146.
Similarly, a line 148 extends from coil 142 to the output side of
an "and" gate 150. Extensions of line 62, carrying the control
pulses at frequency t, comprise one of the two inputs to each of
"and" gates 146 and 150. A line 152 extending from the output of
shift register 54 comprises the second input to "and" gate 150, and
a line 154 comprises the second input to "and" gate 146. As will
appear below, the array of components 132 through 154 are used to
simultaneously deliver each control pulse and each data bit for
transmission across communication means 14 and reception by the
shift register 102 at the receiving side.
The normally open contacts 158 on a relay 156 are serviced by the
lines 122 and 124, and the coil 160 of said relay is suitably
grounded on one side and connected to a line 162 on the other side.
Relay 156 controls the condition of receiving portion 14b as to
whether it will send or receive signals, as will appear in the
Operation section below.
Line 120, which includes a suitable amplifier 164, feeds pulses
from transmitter 14b to a pulse shaper 166 the output of which is
fed on a line 168 to an "or" gate 170. The output line 172 from
"or" gate 170 feeds the R terminal of bistable multivibrator 174
which is called the transmit enable flip-flop. Line 162, feeding
coil 160 of relay 156, is the output line of flip-flop 174. Line
118 from the communication means includes a suitable amplifier 176,
and thereafter breaks into two branch lines, one of which feeds the
set or S terminal of flip-flop 174, and the other one of which
feeds the pulse shaping and time delay means 178. A line 180
connects the output of means 178 to the K terminal of a shift
enable flip-flop 182. The other inputs to flip-flop 182 are a line
184 at its J terminal, and the control pulses at frequency t on
line 62 at its C terminal. A line 186 is connected to the output of
shift enable flip-flop 182.
Line 186 is one of the inputs to an "and" gate 188, the other input
of which is delivered on a line 190. Line 190 connects to the
output of a NAND gate 192. As is known, a NAND gate is an "and"
gate plus an inverter, so that the output will be high at all times
except when all of its inputs are high. Line 184, described above,
including an inverter 194, branches off from line 190, and also
branches off to the J terminal of another flip-flop 196. The K
terminal of flip-flop 196 is connected by a line 198 to the output
of an "and" gate 200. The output of flip-flop 196 is carried on
line 154, described above, which also connects to shift register
54. A three-way branching line 202 interconnects the output of
"and" gate 188, one of the inputs to "and" gate 200, and shift
register 54. Line 190 from NAND gate 192 interconnects the second
input of "and" gate 200, one of the inputs to "and" gate 188, as
described above, and the input of a second pulse shaper and delay
circuit, similar to circuitry 178 described above. A line 206
interconnects the output of circuitry 204 and the second input
terminal of "or" gate 170.
OPERATION
Referring back to FIG. 2, each of the pumps 16 is free to operate
independently of all the others. The clock 42 operates
continuously, continuously driving the counter 48 and the decoder
52. Thus, a circulating triggering pulse is sequentially present on
the lines 30 to the data pulse passing flip-flops 24. It is an
important aspect of the present invention that the frequency of the
triggering pulse on any one of the lines 30 be greater than the
data pulse frequency produced by the pumps 16 at their maximum
speed. A specific example may be helpful in explaining this point.
It is a fair assumption that commercial gasoline vending pumps have
a maximum speed of 12 gallons a minute. As disclosed and explained
in our previous patent mentioned above, it is sufficient to use a
transducer which will produce 10 data pulses per gallon of
gasoline. 100 pulses per gallon could be used if more resolution is
required. Thus, at the pump's top speed, 120 pulses a minute or two
data pulses a second will be produced. In the operating prototype
of the invention, clock 42 produces pulses at the rate of 1,000 per
second. Counter 48 keeps counting these and supplies signals
corresponding to the digits zero through nine on its output lines
50. Therefore, there is a signal on any one line 30 corresponding
to one of the digits zero to nine at the rate of 100 times a
second. Thus, the triggering pulse is present at any one flip-flop
24 at 50 times the maximum rate of speed of the production of data
pulses by the pump 16 associated with that flip-flop.
Because there happened to be five pumps in this example, it is
possible to double the rate of speed of the circulation of
triggering pulses around the flip-flops 24 by using two digits for
each flip-flop. That is, zero and five to control one flip-flop,
one and six to control the next, etc. Not all the digits need be
used, which might be necessary in certain situations, e.g., if
between six and eight pumps are to be included. Other arrangements
will present themselves to those skilled in the art since the
timing means are shared by all the sets of pumps in the station,
only one set being shown.
The data pulses, after being "cleaned-up" by the filter means 20,
pass through the parallel lines 22 and inverter 26 to the input
terminals of flip-flop 24. Since the circulating triggering pulse
is so much faster than the data pulses, the invention assures that
no data pulses will be lost because even if two pumps should
produce a data pulse simultaneously, one will in effect "wait" at
the input to its flip-flop until the triggering pulse circulates
around to allow it through. However, by so providing the speed
difference to assure that no pulses are lost, the equipment has the
potential of counting the same data pulse more than one time. This
potential problem is overcome by providing a one-shot multivibrator
32 of such a character that it responds to only a falling edge of
the output of flip-flop 24. Subsequent triggering pulses on the
line 30 do not cause multiple counting, and the circuit is
independent of the width of the data pulse, because once a
flip-flop 24 is "set" by the simultaneous presence of a raw data
pulse on line 22 and a timing pulse on line 30, it remains "set"
and insensitive to additional timing pulses until it senses the
tail and falling edge of the raw data pulse. The flip-flop resets
after the falling edge occurs and after the next timing pulse
occurs, thereby rendering it ready to receive the next data pulse
while simultaneously driving multivibrator 32 to put out a pulse to
counter 40 via gate 36.
The outputs of the one-shots 32 then pass through the lines 34, the
"or" gate 36 and line 38 to the counter 40. Because the firing of
the one-shots corresponds to the movement of the circulating
triggering pulse on the line 30, and because of the extremely high
response speed of the solid state components used, there is
virtually no possibility of a data pulse being lost in its passage
through the "or" gate 36.
Referring now to FIG. 4, the sets of lines 56 cause shift register
58 to virtually instantaneously follow the count as it proceeds on
all the counters 40. Each section of the shift register 58
associated with each counter operates independently of the other
parts of the shift register during this operation. Nothing further
occurs in the circuitry of FIG. 4 until the data center
interrogates the remote location to request its count. The sequence
of events, thereafter, is:
1. Device 68 must be put in the data mode.
2. The number of the transmitting data set 14b is dialed from the
data receiver 14a (either manually or by computer), connection is
completed, and the receiver data set put in the data mode.
3. Switch 108 is operated momentarily and the transmit command is
generated.
4. Upon receipt of the transmit command from the receiving
circuitry, shift register 54 at the transmitter is isolated from
all counters 40 so that the counters are free to continue
operating, and the shift register holds the one composite number
which will be transmitted.
5. The data is transmitted across the communication means to the
shift register 102.
6. FIG. 4 circuitry is returned to the ready condition.
7. Shift register 54 is reconnected to the counters 40.
Developing these steps in detail, the operation of switch 108
causes flip-flop 112 to change states, and produces a signal on
line 116 feeding one-shot 92. Prior to this occurrence, a signal
was present at terminal Q and line 100, holding contacts 96 of
relay 94 closed. When the one-shot 92 fires, contact Q becomes
activated and contact Q becomes deactivated. Thus, line 90 becomes
conducting, resetting shift register 102 and activating coil 88 of
relay 84. Contacts 86 on said relay open, thus rendering receiver
14a in condition to send the transmit command. Simultaneously, coil
98 of relay 94 becomes deactivated, opening contacts 96, and the
transmit command is sent out across the communication means from
14a to 14b. One-shot 92 then completes its timing cycle,
reactivating terminal Q, deactivating terminal Q, thus deactivating
coil 88, thus allowing contacts 86 to return to their normally
closed position, thus rendering receiving side 14a ready to receive
data.
The above chain of events cause certain corresponding occurrences
on the 14b sending side. Prior to any transmit command, a signal
was automatically generated and was present on line 120. This
signal is produced by transmitter 14b when connection between it
and receiver 14a was completed. The automatically generated signal
is then fed to buffer 164, shaped by device 166, and fed through
"or" gate 170 and through line 172 to reset flip-flop 174. No
signal is thus assured on line 162, rendering coil 160 deactivated
and contacts 158 in their normally open condition. When contacts
158 are open, transmitter portion 14b is ready to receive the
transmit command signal. Upon receipt of the transmit command
signal from 14a at 14b, that signal is present on line 118, is fed
through gate 176, and proceeds to perform two functions along the
parallel branch lines 118. Firstly, the transmit command changes
the state of flip-flop 174 to its set condition, creating a holding
voltage on line 162, and closing contacts 158 by the chain of
events described above. Lines 122 and 124 are thus shorted
rendering transmitter 14b in condition to transmit data.
Simultaneously, the transmit command signal is sent to pulse
shaping and time delay circuitry 178. A delay is required because
the remaining equipment described below is all solid state, whereas
the enabling equipment described above includes mechanical relays
which require longer periods of time to operate. After the delay,
the transmit command proceeds on line 180 to the K terminal of the
shift enable flip-flop 182, thus causing output line 186 to
conduct. "And" gate 200, when activated by signals on its two input
lines 202 and 190, provides a signal on its output line 198 to
isolate shift register 54 from the counters 40 via flip-flop 196
prior to data transmission from 14b to 14a. As will appear below,
the same components operate to reconnect shift register 54 to the
counters 40 at the end of data transmission. "And" gate 188, which
is actually a NAND gate, is needed for a signal inversion, and in
other embodiments it could be omitted if such an inversion is not
required.
NAND gate 192 is high at all times except at the end of the shift
when it momentarily goes low. This is so because the input to gate
192 is the binary coded numbers corresponding to the count it is
desired to transmit. Since each stage is limited to a count of
nine, and since all the inputs from any stage could be conducting
only if that one stage were thereby producing a set of signals
corresponding to the number 15, then it is certain that there will
always be at least one signal in each set of four from each stage
which will be low or a "zero" in binary jargon. So long as even one
input to gate 192 is low, then the output of the gate will be high.
To insure this desideratum, by means described below, there is
inserted a binary zero behind the data prior to transmission. Since
there is a signal on line 190 there is a signal to one of the
inputs to each of "and" gates 188 and 200. When flip-flop 182
receives an input on its K terminal, the second input to "and" gate
188 is present causing it to produce an output on line 202, causing
the second input to be present on "and" gate 200, causing flip-flop
196 to receive an input on its K terminal. A signal is then present
on line 154 from the output of flip-flop 196, causing two different
chain of events in the circuitry. First, the output of 196 on the
vertical leg of line 154 to the shift register 54 provides an
initial 0 followed by a series of 1 s which follow the data through
shift register 54 during data transmission. The other branch of
line 154 provides a 1 gating signal to "and" gate 146 which allows
fiducial, control, or clock pulses to flow into the data set
14b.
Now the continuously supplied control pulses on line 62 at
frequency t feeding shift register 54 and "and" gates 146 and 150,
and relays 132 and 134 causes the data and a train of fiducial or
gated control pulses to be transmitted from 14b to 14a and on to
lines 80 and 82 to the shift register 102 at the data center.
A shift register is well known in the art. However, the following
analogy may be helpful to illustrate its operation and to better
explain the manner of operation of the invention. The shift
register may be thought of as a corridor in which a line of
soldiers of no more than a certain number can stand single file.
The soldiers correspond to the data bits which may be either high
or low, one or zero in binary nomenclature. If another soldier
pushes in at one end of the line then one soldier will be forced
out at the opposite end of the line. Applying this analogy in the
present invention, the control pulses, all high, feeding in at the
right hand side on line 62 one by one push the data pulses out the
left hand end on line 52 feeding "and" gate 150. The first data
pulses will be the station identification number. When all the data
bits have been replaced by control pulses, all high or 1 s, then
the circuitry will reset, as will be explained below.
Each data bit, or absence of a data bit, is transmitted by
operating or not operating coil 142 of relay 134. Simultaneously,
at the rate of speed determined by the control pulse frequency t a
fiducial will definitely be transmitted by operating the coil 138
relay 132. Each control pulse on line 62 is one input to both "and"
gates 146 and 150, since a steady signal is present on line 154,
relay 132 will operate to send out a fiducial on line 126
corresponding to each control pulse. In the event there is a high
data bit on line 152, the communication means 14 will
simultaneously transmit it since relay 134 will operate to send
that high data bit out on line 130.
After all the data is thus shifted out, NAND gate 192 momentarily
goes low since all its inputs are high, the shift register is full
of 1 s, and line 190 momentarily stops conducting. Inverter 194
activates the two branch lines 184 to cause the two flip-flops 182
and 196 to change back to their "set" or ready states. Line 186
thus stops conducting, thus deactivating "and" gates 188 and 200,
as well as reconnecting the shift register 54 to the counter 40 by
means of the absence of a signal on line 202.
Line 190 deactivating provides a pulse to component 204, and after
the delay thereof, puts transmitter 14b into a state ready to
receive the next transmit command to initiate the next transmission
cycle. This resetting occurs via line 206, gate 170, line 172,
flip-flop 174, line 162, and to relay 156 to open the connection
between lines 122 and 124. The delay of component 204 is provided
to assure that the last data bit is sent out by relays 132 and 134
before the transmitter is reset as described above.
In the particular application of retail gasoline marketing
described herein, relatively slow timing (in the milliseconds to
microseconds range) is all that is required, thus permitting the
use of relatively inexpensive logic circuitry. Another associated
advantage is that the embodiment of the invention described lends
itself to implementation by large scale integrated circuitry, which
yields the advantages of still smaller size, high reliability and
low power consumption.
While the invention has been described in detail above, it is to be
understood that this detailed description is by way of example
only, and the protection granted is to be limited only within the
spirit of the invention and the scope of the following claims.
* * * * *