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Claims  |
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What is claimed is:
1. A device for the metering of encrypted postage and similar indicia
comprising:
(a) an entry means for the entry of data corresponding to alphanumeric
characters;
(b) means coupled to said entry means for the storage of said data;
(c) an encryption circuit for developing a code word of a plurality of code
characters from data in the storage means corresponding to a plurality of
said alphanumeric characters;
(d) means for imprinting a bar-code representation of the data applied
thereto; and
(e) selection means having an output coupled to said imprinting means and
coupled to receive data from said storage means and said encryption
circuit for alternately feeding data of said storage means and a code word
of said encryption circuit to said imprinting means to control the
imprinting means to imprint a bar-code indicia having intermixed portions
corresponding to alphanumeric characters and said code characters
respectively, the code word providing verification of the validity of the
indicia.
2. A device as in claim 1 wherein said imprinting means includes a dot
matrix printer for imprinting bar codes on a printing medium.
3. A device according to claim 2 wherein said entry means comprises a
keyboard and wherein said keyboard is coupled to means for moving the
printing medium past said dot matrix printer.
4. A device according to claim 3 wherein said printing medium is a package,
said system further comprising timing means coupled to said moving means
for synchronizing said alternate feeding with the position of said
package.
5. A system for the printing and reading of encrypted messages on a
printing medium, the system comprising:
(a) a keyboard for the entry of data corresponding to alphanumeric
characters;
(b) means coupled to said keyboard for storing the data;
(c) encryption means responsive to the data for producing a code of a
plurality of code characters derived from the data and corresponding to a
plurality of said alphanumeric characters;
(d) a bar-code printer for printing a bar-code indicia on said medium;
(e) means coupled to said storage means for driving said printer to
intermix signals applied thereto corresponding to an alphanumeric
character from said keyboard and signals corresponding to one of said code
characters, whereby said indicia is formed of intermixed portions
corresponding to said alphanumeric characters and code characters;
(f) means for reading said bar-code indicia on said medium;
(g) means coupled to said reading means for generating first signals
corresponding to a decryption of said code and second signals
corresponding to the portions of said bar-code indicia corresponding to
said data; and
(h) means for comparing said first and second signals for verification of
said bar-code indicia.
6. A system according to claim 5 wherein said printer includes a printhead
and means for moving said medium past said printhead.
7. A system according to claim 6 wherein said moving means includes means
responsive to positions of said medium for synchronizing said printer
driving means with the movement of said medium.
8. A system according to claim 7 wherein said reading means includes a
reading head for sensing indicia on said medium, means for translating
said medium past said reading head, and means responsive to the position
of said medium for timing said alternate driving means.
9. A device for verifying a bar-code indicia including postal data and
encrypted material derived from said postal data, said inidicia being
printed on a printing medium comprising:
(a) means for reading bar-code indicia on said printing medium said indicia
having alternately appearing intermixed portions corresponding to postal
data and encrypted material respectively;
(b) means responsive to bar-code indicia read by said reading means for
generating signals corresponding to the data and the encrypted material;
and
(c) means for comparing said signals to verify the indicia.
10. A device according to claim 9 further comprising means synchronized
with reading by said reading means for moving the printing medium past a
reading head of said reading means.
11. A package having a postage indicia imprint supported thereon including
a means for validating the integrity of the indicia, the indicia
comprising:
(a) a first uncoded bar-code indicia portion representing the value of the
imprint, said value corresponding to a postal amount for the mailing of
said package,
(b) a second bar-code indicia portion for indicating other information,
portions of the first and second indicia portions being imprinted in
intermixed segments on said package,
(c) the second indicia portion being an encrypted function of said value,
the encrypted message providing information validating the integrity of
the postage indicia.
12. A package having an imprint supported thereon and comprising:
a bar-code indicia having a first portion representing the value of the
imprint, and a second portion representing an encryption of the value and
other information on the package, with portions of said first and second
portions being intermixed and imprinted on the package, the encryption
being an indication that the imprint is valid, the value of the imprint
representing a postal value for the mailing of the package.
13. In a postage meter, a system for providing validation information to a
bar-code postage imprint produced by the meter, the validation system
comprising:
(a) bar-code printing means,
(b) means coupled to the printing means for controlling the operation of
the printing means, and
(c) means coupled to the controlling means for alternately applying
bar-code data corresponding to postal information and encryption data
dependent upon the postal information to said controlling means, said
controlling means comprising means for controlling said printing means to
print a bar-code imprint having a sequence of intermixed portions
representative of the postal information and encryption data respectively,
to provide an indication that the postage imprint is valid.
14. A system as in claim 13 in which the printing means is a thermal
printer.
15. A system as in claim 13 in which the postage imprint includes postage
amount and in which the means coupled to the controlling means includes
means for processing a postage amount to provide the encryption data.
16. A system as in claim 13 in which the postage imprint includes zip code
information and in which the means coupled to the controlling means
includes means for processing the zip code information to provide the
encryption data.
17. A system as in claim 13 in which the postage imprint includes a date
and in which the means coupled to the controlling means includes means for
processing the date to provide the encryption data.
18. The system as in claim 13 in which the postage imprint includes a
postage amount, zip code information, a date and a serial number.
19. The system as in claim 18 in which the means coupled to the controlling
means includes means for processing the postage amount, the zip code
information, the date and the serial number to provide said encryption
data.
20. In a method for printing postal indicia that includes postal
information on a mailpiece comprising employing a device including a
bar-code printing means and a means for controlling the printing means,
the method of validating the postal indicia comprising the steps of:
(a) generating encryption data dependent upon said postal information; and
(b) controlling the operation of the printing means to print a bar-code
indicia with a multiple sequence of separate adjacent portions that
alternately represent the encryption data and said postal information.
21. The method as in claim 20 in which the postal information comprises a
value, further including the step of printing the value in a bar code
along with the encryption data on the mailpiece.
22. A system for the reading of encrypted messages on a printing medium,
the encrypted message being provided on a bar-code indicia having adjacent
bar code portions that represent a plurality of alternating data and
encrypted material, the system comprising:
(a) means for reading said bar-code indicia on said medium;
(b) coding means coupled to said reading means for generating code signals
and means for generating second signal, representing said bar code
indicia; and
(c) means for comparing a code read by said reading means with said second
signal at a determined time for verification of said bar-code indicia.
23. A device for the metering of postage and similar indicia, comprising:
entry means for the entry of data signals corresponding to sequences of
alphanumeric characters related to the mailing of a package,
encoding means coupled to receive said first signals and produce coded
signals corresponding thereto,
a bar-code printer,
drive means for driving a material to be printed with respect to said bar
code printer, and
synchronizing means connected to apply a plurality of said data signals and
said coded signals alternately to said bar code printer to print an
indicia in which a plurality of alternate adjacent portions thereof
represent said data signals and said coded signals.
24. The method of metering of postage and similar indicia, comprising:
inputting data signals corresponding to postal information,
encoding said data signals to produce coded signals, and alternately
applying said data signals and said coded signals to a bar code printer
for printing indicia on a piece of mail having a sequence of bar code
portions with multiple adjacent portions thereof alternately representing
a plurality of said data signals and said coded signals. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
This invention relates to devices for the metering of postage and similar
indicia and, more particularly, to a metering device including electronic
circuitry for the encryption of the indicia to be printed.
Reference is hereby made to copending related patent applications assigned
to the same assignee as this application; application of John Clark
entitled "System Having A Character Generator For Printing Encrypted
Messages", Ser. No. 515,073, filed on July 18, 1983, application of John
Clark and Daniel Dlugos entitled "System For Printing Encrypted Messages
With A Character Generator And Bar-Code Representation", Ser. No. 515,072,
filed on July 18, 1983, and application of John Clark, Alton Eckert and
David Warren entitled "System For Printing And Reading Of Encrypted
Messages", Ser. No. 515,760, filed on July 21, 1983.
Postage meters find extensive use, both in the United States and abroad,
for imprinting postage on objects to be mailed. The postage may be applied
by a self-sticking label which is imprinted by a print head enclosed
within the meter, the label then being placed in adhering contact on the
letter, parcel or other object to be mailed. Alternatively, the postage
may be printed directly on the outer wrapping of the object being mailed.
The printing apparatus is also capable of printing a short message in
addition to the amounts of the postage so that, if desired, the meter can
be used for the imprinting of suitable indicia designating instructions
and/or routing for transport by private carrier as well as by the mail.
Furthermore, if desired, the meter may be utilized for the imprinting of
yet other forms of labels, such as tax stamps, assuming that governmental
approval for such tax stamps is obtained.
A serious problem which has been encountered in the use of imprinted
postage is the fradulent adulteration of such postage labels whereby, in
effect, the person adulterating the postage is stealing postage. A
fraudulent label may enable someone to obtain postage, or in the case of a
tax stamp, to avoid paying the tax.
SUMMARY OF THE INVENTION
The foregoing problem is overcome and other advantages are provided by a
device for the metering of postage and similar indicia. The device
includes electronic circuitry for the development of encryption symbology,
and a print head which is driven by the electronic circuitry to imprint
both the postage, or other indicia, in combination with the encryption
markings. The indicia are printed in the form of a bar code wherein a set
of bars is used to communicate data while a further set of bars is used to
communicate encrypted material for a code word. The two sets of bars are
encrypted serially so that they can be readily identified by a single
bar-code reader for extraction of the characters which communicate the
message and for the characters which communicate the code. An important
feature of the electronic circuitry for performing the encryption process
is the incorporation into the circuitry of a means for altering the
encryption process in accordance with the amount of postage, the date,
and, if desired, the sender and other data. Thereby, the message imprinted
on the label is related to the encryption markings. In the event that the
message is altered, either the encryption markings cannot be decoded or,
if decoded, the resulting legend does not agree with the legend imprinted
on the label.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the invention are explained in
the following description, taken in connection with the accompanying
drawings wherein:
FIG. 1 shows a system incorporating the invention by imprinting delivery
data, such as postage, on a package by a dot matrix printer wherein the
positions of the dots have been offset to create voids as a security code;
FIG. 2 shows the arrangement of dots in a 7.times.5 matrix superposed upon
a grid for identifying voids produced by displacement of the dots;
FIG. 3A is a block diagram of a first embodiment of a print system of FIG.
1 utilizing a variable void coding;
FIG. 3B is a block diagram of a second embodiment of the print system of
FIG. 1 utilizing additional alphanumeric characters for the coding;
FIG. 3C is a block of a third embodiment of the print system of FIG. 1
utilizing a bar-code form of indicia;
FIG. 3D is a block diagram of a fourth embodiment of the print system of
FIG. 1 combining features of FIGS. 3B and 3C;
FIG. 3E shows a modification of the system of FIG. 3A for the interleaving
of code and indicia by speckling;
FIG. 4A is a block diagram of a first embodiment of a read system of FIG. 1
utilizing the variable void coding;
FIG. 4B is a block diagram of a second embodiment of the read system of
FIG. 1 for coding implemented by additional alphanumeric characters;
FIG. 4C is a block diagram of a third embodiment of the read system of FIG.
1 for use with bar-code indicia;
FIG. 4D is a block diagram of a fourth embodiment of the read system of
FIG. 1 combining features of FIGS. 4B and 4C; and
FIG. 4E shows a modification of the system of FIG. 4A for the interleaving
of code and indicia by speckling; and
FIG. 5 is a block diagram of a coder utilized in the systems of FIGS. 3A-D
and 4A-D.
FIG. 6 shows a field of logic 1's and 0's for the embodiment of FIGS. 3E
and 4E.
DETAILED DESCRIPTION
In FIG. 1, a system 20 incorporates the invention for the transmission of a
mailpiece or package 22 from a sending station 24 via a delivery system 26
to a receiving station 28. The term "package" is used only by way of
example to illustrate the variety of objects which are sent from one
location to another, both by use of the mail and by private carrier. Thus,
the term "package" includes mailpieces such as letters, flats, envelopes,
parcels and other objects which are sent via the mail, and have a surface
for receipt of imprintings of postage and/or other indicia including
messages. The term "package" also includes labels in those situations
wherein the indicia or message is imprinted on a label which is then
affixed to a mailpiece, in the case of postage, or to some other object
such as bottle wherein the label is a tax stamp. The delivery system 26
may be any one of a number of systems such as, for example, a parcel
delivery service or the postal service. The portrayal of the system 20 in
FIG. 1 is stylized to facilitate explanation of the invention, with
portions of the stations 24 and 28 being cut away to show components
thereof utilized in the imprinting and reading of data on the outer cover,
such as an envelope, of the mailpiece 22.
In accordance with the invention, the data is encrypted to ensure the
validity of the data. The data includes, typically, the fee or postage,
the date, a serial number of the sending station 24, and, if desired, a
zip code or other form of routing code for automated sorting of the
mailpieces 22. The encryption is accomplished by coding circuitry, to be
described hereinafter, which utilizes a seed word in developing the code.
The seed word is obtained from a base seed word 30 placed in both the
sending station 24 and the receiving station 28, the base seed word 30
being altered in a manner to be described, in accordance with the date,
the fee, and the serial number of the sending station 24 to provide the
seed word utilized by the coding circuitry. The sending station 24
includes a print system 32 for imprinting the data on the mailpiece 22,
while the receiving station 28 incorporates a corresponding read system 34
for reading the data imprinting on the mailpiece 22.
The print system 32 comprises a matrix printer 36 which includes a well
known set of electronically actuated dot printing points in a printing
head which, in accordance with electrical signals applied to respective
ones of the points, imprints a row of dots which represent a portion of a
letter, numeral, or other character. For example, such a printing head may
incorporate ink jets or, alternatively, may employ heat or light in the
case wherein heat-sensitive labels or light-sensitive labels are utilized.
The mailpiece 22 is moved along a platform 38 of the sending station 24 by
a roller 40, the roller 40 advancing the mailpiece 22 beneath the matrix
printer 36 as the printer 36 imprints a succession of dots on the cover of
the mailpiece 22. A sensor 42 detects the presence of the package 22 for
activating the roller 40. The sensor 42 may have the form of any of a
number of well known package sensors, to incorporate, for example, an
electric eye or a roller which makes electrical contact with the roller
40. Thereby, a breaking of the light beam, or a breaking of the electric
current signals the presence of the package 22 for activation of the
roller 40 to advance the package 22. The roller 40 and the matrix printer
36 are positioned by means of a frame 44 within the sending station 24.
The receiving station 28 also incorporates a roller 40 and a sensor 42 for
advancing a package along a platform 38. A connector 43, shown in phantom
inside the sending station 24, is coupled to the sensor 42 for counting
output signals of the sensor 42 to provide a count of the respective
packages 22 sensed by the sensor 42. The read system 34 includes a matrix
sensor 46, the sensor 46 comprising a set of well known photo-electric
sensors which are arranged along a row and positioned by a frame 44 as
described previously for the sending station 24. The positions of the
photo-electric sensors of the matrix sensor 46 corresponds to the
positions of the print points of the matrix printer 36 so that the
presence and absence of markings of the printer 36 can be sensed by the
matrix sensor 46.
The sending station 24 further comprises a keyboard 48 and an alphanumeric
display 50. The keyboard 48 includes function keys which identify the
nature of the data which is being entered by data entry keys of the
keyboard 48. Thus, for example, individual ones of the function keys are
employed to identify the date, the amount of the fee, and routing data.
The data to be entered appears in the display 50 after which it is entered
into the electronic circuitry of the sending station 24 by pushing an
enter key of the keyboard 48. The receiving station 28 also incorporates
displays, there being a data display 52 as well as a verification display
54 which indicates that the message imprinted on the package 22 has been
verified or that it has been obliterated so as to prevent verification.
With reference also to FIG. 2, there is shown a mode of encripting
alphanumeric characters of the message imprinted on the mailpiece 22. This
mode of encryption, which may be referred to as variable void coding is
accomplished by offsetting the dots imprinted by respective printing
points of the printer 36 so as to create voids at locations which would
normally, in the absence of encryption, have imprinted dot. The field of
dots in FIG. 2 is defined by a matrix of seven rows by five columns. Such
a matrix is a standard matrix in the printing industry and, accordingly,
is most readily employed in a postage meter or similar device for the
imprinting of postage and transportation data on a mailpiece. While the
invention is useful for fields of both larger and smaller arrays of dots
than that disclosed in FIG. 2, in order to facilitate explanation of the
invention, it is to be assumed in the ensuing description that the
7.times.5 matrix is to be employed. Individual ones of the dots in FIG. 2
are identified by the legends 56 while two exemplary displaced dots 56A
and 56B are disclosed in phantom. The phantom view indicates the postions
which a dot 56 would occupy in the presence of encryption, the normal
position, indicated by solid lines, being present in the absence of
encryption. In particular, it is noted that the displacement associated
with the encryption provides a void equal to one-half the width of the dot
56. Thus, as may be seen in the cross-bar of the letter "A" depicted in
FIG. 2, the offsetting of the dot 56B enlarges the space between
neighboring dots, to the left of the dot 56B, while decreasing the space,
between neighboring dots, to the right of the dot 56B. Accordingly, the
void or space between one pair of neighboring dots is increased while the
void or space between another set of neighboring dots is decreased. In the
encryption process, only a relatively few of the dots of an alphanumeric
character are so displaced, the remaining dots maintaining their regular
positions to permit identification of the character imprinted on the
mailpiece 22.
In accordance with a feature of the invention, a reference character
without the displaced dots of the encryption process is compared to a
received character having the displaced dots associated with the
encryption process. The differences between the characters is thus a
statement of the code.
FIG. 2 also shows a grid 58 superposed on the character "A" to explain the
operation of the matrix sensor 46. The spacing between photoelectric
elements of the matrix sensor 46 corresponds to the spacing between the
rows of the grid 58, the horizontal lines being parallel to the arrow 60
which designates the direction of movement of the mailpiece 22. The
spacing between the rows of the grid 58 is smaller than the spacing
between centers of the elements of the matrix sensor 56 so as to permit
the reading of the dots or other shaped markings of the character
imprinted by the printer 36. Similarly, the rate of reading by the matrix
sensor 46 is increased to provide a spacing between columns of the grid 58
which is smaller than the spacing between the dots of the printed
character so that the matrix sensor 46 is able to respond to the
variations in spacing between the dots resulting from the displacement
associated with the encryption. By way of example, the spacings depicted
between centers of the dots of the character in FIG. 2 are four times the
spacing of the cells of the grid 58. Correspondingly, the grid 58 provides
the read system 34 with a resolution four times that of the print system
32, and thereby enables the read system 34 to function even with
characters that may have become partially obliterated, as well as in the
situation wherein the alignment of the package 22 on the platform 38 in
the receiving station 28 does not correspond precisely to the
corresponding alignment in the sending station 24.
With reference now to FIG. 3A, there is provided a more detailed
description of the components of the print system 32 of FIG. 1. The drum
40 is mechanically coupled via a line 62 to drive unit 64 which rotates
the drum 40 for advancement of the mailpiece 22. The same form of drive
unit 64 is also provided in the read system 34 of FIG. 4A, as will be
described subsequently, for rotation of the drum 40 therein. The drive
unit 64 comprises the mailpiece sensor 42, a motor drive circuit 66, a
stepping motor 68, a gear train 70 mechanically coupled via a dashed line
72 to the motor 68, a shaft-angle pulser 74 also mechanically coupled via
the line 72 to the motor 68, and an address counter 76.
In operation, the motor 68 is energized by the drive circuit 66 for
rotation of the drum 40 via the gear train 70. The drive circuit 66 is
triggered into operation by the sensor 42, and continues to operate the
motor 68 until the sensor 42 ceases to sense the presence of the mailpiece
22. Thereby, the drum 40 is made to rotate a sufficient amount to move the
mailpiece 22 past the drum 40. The momentum of the mailpiece 22 then
carries it through the sending station 24, as well as through the
receiving station 28 as will be described substantively with respect to
FIG. 4A. The gear train 70 reduces the rate of rotation of the drum 40 to
a much slower value than the rate of rotation of the output shaft of the
motor 68 on line 72. Th shaft-angle pulser 74 comprises well known
circuitry such as that of a tachometer or encoder for providing an output
electrical pulse to the counter 76 for each increment in rotation of the
output shaft of the motor 68. Since the pulser 74 is mechanically locked
to the drum 40 by the gear train 70, a counting by the address counter 76
provides a count which corresponds precisely to the position of the
mailpiece 22 on the platform 38 of the sending station 24. The leading
edge of the electric output signals of the sensor 42 on line 78 resets the
counter 76 back to zero upon the arrival of the next mailpiece 22 at the
sensor 42. The output count of the counter 76 will be utilized, as
described hereinafter, for addressing components of the print system 32
for operation of the matrix printer 36.
The print system 32 further comprises an address generator 80, a timing
unit 82, an address generator 84, a RAM 86 (random access memory) for the
storage of data entered from other components including the keyboard 48
and the counter 43, a coder 88 for providing the encripting code as will
be more fully described in FIG. 5, a memory 90, a memory 92, and a set of
void units 94 for driving respective ones of a set of print points 96 of
the matrix pointer 36. Each void unit 94 is utilized for incorporating
digits of the encryption code which are stored in the memory 92 into the
printing process for displacing dots of the character matrix in accordance
with the variable-void feature of the invention. Each void unit 94
comprises a shift register 98, two AND-gates 101-102, and an OR gate 103.
In the AND gate 102, 1 of the input terminals thereof is complimented,
this terminal being coupled along with a corresponding terminal (not
complimented) of the gate 101 to the code memory 92.
In operation, a person utilizing the sending station 24 enters data into
the RAM 86 by use of the keys of the keyboard 48. As has been noted
hereinabove, the keyboard 48 is also coupled to the display 50 for
displaying the data which is to be entered into the RAM 86. During entry
of the data, the signals of the keys of the keyboard 48 are also applied
to the address generator 80 to activate the generator 80 to address the
RAM 86 to designate the locations wherein the data of the keyboard 48 is
to be stored within the RAM 86. The generator 80 is also utilized for
addressing the RAM 86 during the outputting of data from the RAM 86 to the
coder 88 and to the memory 90, the action of the generator 80 initiated by
signals of the timing unit 82 during the outputting of the storage data.
The timing unit 82 also initiates activity of the address generator 84 to
designate locations within the memory 90 for receiving data from the RAM
86. The coder 88 utilizes the data of the RAM 86 in providing the digits
which are stored in the code memory 92, and the memory 90 is utilized for
applying the data of the RAM 86 via the void units 94 to the print points
96 of the matrix printer 36.
During the first stage of the operation of the sending station 24, the data
such as the amount of postage, the routing as via zip code, the date and
the package count of the counter 43 are entered into the RAM 86 for the
subsequent imprinting of a message on the package 22. The message includes
the date, the package count, the serial number of the sending station 24,
the delivery fee or postage, and optionally zip code and/or city, state of
the origination. In accordance with the invention, the messsage also
includes, in encrypted form, a verification of the message showing that
the message was indeed printed by the sending station 24, and not by an
impostor.
Accordingly, the second stage in the operation is the transfer of data from
the RAM 86 to the coder 88 for the generation of the encrypted
verification, and to the memory 90 for operation of the matrix printer 36.
The first two stages are initiated sequentially in response to the
aforementioned signals of the timing unit 82 to the generators 80 and 84.
During the second stage of the operation, the coder 88 generates the
requisite code and applies the digits for control of the encryption
process to the code memory 92 in a manner to be described subsequently
with reference to FIG. 5.
The third stage of the operation begins when the package sensor 42 has
detected the presence of a mailpiece 22 or other object such as a letter
which is to be mailed. As has been noted above, the sensor 42 resets the
counter 76 and initiates operation of the motor drive circuit 66 with the
resultant counting of the counter 76. The counter 76 counts out successive
addresses of both the print memory 90 and the code memory 92 for
transferring the data contained therein to the matrix printer 36. During
the transfer of data from the RAM 86 to the memory 90, the data is
arranged in accordance with the rows of dots of the matrix of each
character which is to be imprinted on the mailpiece 22. Thus, in response
to each designation of character by the keyboard 48, the RAM 86 makes
available to the memory 90 the succession of dots for each row of the
characters matrix as has been explained with reference to FIG. 2.
Accordingly, upon transfer of the data from the RAM 86 to individual
sections of the print memory 90, respective sections of the memory 90
store the requisite sequence of dots which are to be applied by the
corresponding print points 96 to the mailpiece 22 during the printing
operation.
In response to the addressing by the counter 76, the data is read out of
the respective section of the memory 90 and of the respective sections of
the memory 92 into the corresponding void units 94 for application to the
corresponding printheads 96. With respect to the operation of the void
units 94, each void unit 94 operates in the same manner. In each void unit
94, data from the memory 90 is applied to an input terminal of the shift
register 98 through which it is clocked at a higher rate than the entry of
data from the memory 90 into the register 98. For example, the rate of
clocking in the register 98 may be at a rate four times greater than the
rate of entry of the data from the memory 90 into the register 98. The
clocking is accomplished in response to clock pulses applied at terminal C
from a clock (not shown) within the timing unit 82.
The foregoing factor of four in the clock rate corresponds to the factor of
four (described in FIG. 2) between a dot of the printed character and a
cell of the grid 58. Thus, as a digital signal enters the shift register
98 from the memory 90, the digital signal then propagates rapidly through
the shift register 98 through successive cells thereof. As these digital
signals propagate through the shift register 98, the mailpiece 22 is
advanced by rotation of the drum 40. Each increment in time associated
with the propagation from cell to cell of the shift register 98
corresponds to an increment in position of the package 22. Each cell of
the register 98 is provided with an output tap or terminal whereby a
signal can be extracted after a predetermined amount of delay from the
time of transfer of the signal from the memory 90 to the shifrt register
98.
Each row of the code memory 92 is coupled to a corresponding one of the
void units 94. More specifically, as has been described above, in each
void unit 94, an output line of the code memory 92 is applied to an input
terminal of each of the gates 101-102. In response to the outputting of a
logic 0 signal from the code memory 92, the AND gate 102 is activated due
to the complementing of its input terminal coupled to the memory 92. With
the activating of the AND gate 102, the digital signals of the shift
register 98 are coupled via the AND gate 102 and the OR gate 103 to the
print point 96. In response to the outputting of a logic 1 signal from the
code memory 92, the AND gate 102 is deactivated and the AND gate 101 is
activated to pass a digital signal from the shift register 98 via the OR
gate 103 to the printhead 96. Since the AND gate 101 is coupled to a cell
of the register 98 downstream from the connection of the AND gate 102 to a
cell of the register 98, the activation of the gate 101 results in a delay
of the operation of the print point 96. In view of the continuous motion
of the package 92 by the rotation of the drum 40, the delay introduced by
the gate 101 results in a displacement of the position of the dots, such
as the previously described displacement of the dots 56A-B of FIG. 2. In
view of the ratio of four cells of the grid 58 corresponding to the
spacing between centers of the dots 56 of FIG. 2, the delay of one of the
registers 98 (as depicted by the connections of the gates 101 and 102 to
the register 98) provides for a displacement equal to one-half the width
of a dot 56 as depicted in FIG. 2. Accordingly, for each occurrence of a
logic 1 from the code memory 92, there is presented a corresponding
displacement in the position of a dot of the character in FIG. 2. For ease
of portraying such displacements, only two s | | |
