U.S. patent number 3,691,353 [Application Number 05/097,648] was granted by the patent office on 1972-09-12 for multimode counting device.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to Jimmie A. Michaud.
United States Patent |
3,691,353 |
Michaud |
September 12, 1972 |
MULTIMODE COUNTING DEVICE
Abstract
A multimode counting device that utilizes number incrementing
and number decrementing signals to change the value of a stored
number. The counting device includes a storage register and
switching or gating circuitry that causes the device to switch
between a first mode of operation for altering a stored number
having a positive polarity and a second mode of operation for
altering a stored number having a negative polarity. The device
also includes additional gating circuitry responsive to the stored
number and to signals in transmission to the storage register to
initiate a change in the operating mode when the stored number is
unity and a signal that will cause that number to become zero is in
transmission to that register instead of waiting until the stored
number actually reaches zero.
Inventors: |
Michaud; Jimmie A. (Dayton,
OH) |
Assignee: |
The Bendix Corporation
(N/A)
|
Family
ID: |
22264465 |
Appl.
No.: |
05/097,648 |
Filed: |
December 14, 1970 |
Current U.S.
Class: |
377/55;
377/45 |
Current CPC
Class: |
H03K
23/56 (20130101); H03K 21/00 (20130101) |
Current International
Class: |
H03K
23/00 (20060101); H03K 23/56 (20060101); H03K
21/00 (20060101); H03k 021/02 (); G06m
003/14 () |
Field of
Search: |
;235/92EV,92LG ;328/44
;307/222 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wilbur; Maynard R.
Assistant Examiner: Thesz, Jr.; Joseph M.
Claims
Having thus described an embodiment of this invention, what is
claimed is:
1. In a multimode counting and number storing system utilizing
number changing signals to change the value of a stored number,
said system including:
number storing means, said number storing means providing magnitude
signals indicating the magnitude of the stored number;
means for transmitting number changing signals to said number
storing means;
means for generating a count direction signal that indicates
whether a number changing signal in transmission to said number
storing means will cause the magnitude of said stored number to be
incremented or decremented;
mode determining means for switching the mode of operation of said
system between a first mode for altering a positive polarity
number, and a second mode for altering a negative polarity
number,
the improvement comprising:
enabling means responsive to said count direction signal and said
magnitude signal for providing an output signal that enables said
mode determining means to switch the operating mode of said system
upon the receipt of signals indicating that said stored number has
a magnitude of unity and that a signal that will cause said stored
number to have a value of zero is in transmission to said number
storing means, a change in the operating mode thereby being
initiated at a time when it is determined that said stored number
will have a value of zero, and before the stored number actually
obtains said zero value.
2. The multimode system set forth in claim 1 in which said enabling
means comprises gating means for transmitting said enabling output
signal to said mode determining means upon the receipt of signals
by said enabling means indicating that the magnitude of said stored
number will be decremented by a signal in transmission to said
number storing means and that the magnitude of said stored number
is unity.
3. The multimode system set forth in claim 1 in which:
said means for generating count direction signals provides a
direction signal for each number changing signal in transmission to
said number storing means;
and in which said enabling means includes:
gating means connected to receive said count direction signals, and
said number changing signals; and
means for delaying the transmission of at least one of said signals
to said gating means so that each number changing signal and its
associated direction signal will arrive at said gating means at
substantially the same time to permit only a signal that will cause
the stored number to have a zero value to cause said enabling means
to transmit an enabling signal to said mode determining means.
4. The multimode system set forth in claim 3 in which:
said enabling gating means also receives said magnitude signals;
and
said delay means delays the transmission of signals to said gating
means so that a signal indicating the magnitude of said stored
number to be unity, and the number changing signal that will change
the stored number from unity both arrive at said gating means at
substantially the same time to prevent an erroneous transmission of
an enabling signal.
5. The multimode counting and number storage device set forth in
claim 1 in which:
said mode determining means receives number changing signals from
said transmitting means and enabling signals from said enabling
means, and provides an output that causes the said system to
operate when enabled by an enabling signal that is in accordance
with a received number changing signal;
said enabling means includes gating means connected to receive
signals from said transmitting means at a position downstream from
the position at which said mode determining means receives signals
from said transmitting means; and
said enabling gating means transmits an enabling signal only when
no signal is received from said downstream position, said enabling
means thereby preventing said mode determining means from
responding to any number changing signal that will cause said
stored number to have a zero value and causing said system to
operate in a mode determined by said zero causing signal instead by
the number changing signal following said zero causing signal.
6. A method of determining the proper counting mode for changing a
stored number of a particular polarity in response to number
changing signals comprising the steps of:
transmitting number changing signals in a sequence to a number
storing means constructed to change the value of the stored number
in response to said received number changing signals;
generating signals indicating the magnitude of the stored
number;
generating a count direction signal for each number changing signal
in transmission to the said storing means that indicates whether
the number changing signal will cause the magnitude of the stored
number to be incremented or decremented;
initiating the generation of a mode determining signal when the
magnitude of the stored number is unity and a number changing
signal is in transmission to said storing means that will cause the
magnitude of the stored number to be zero; and
generating said mode determining signal in accordance with the
number changing signal immediately following the number changing
signal that will cause the value of the stored number to be zero,
said mode determining signal causing counting to be performed in a
first mode for altering a positive polarity number when said
following signal is a number incrementing signal and causing
counting to be performed in a second mode for altering a negative
polarity number when said following signal is a number decrementing
signal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
Electronic counting devices.
2. Brief Description of the Prior Art
Multimode counting devices are known. Any device capable of
utilizing number incrementing and number decrementing signals to
change the value of a stored number that can have either a positive
or a negative polarity must be constructed to operate in two modes.
That is, a number incrementing signal or signal that will cause the
actual value of the stored number to be increased must increase the
magnitude, or absolute value of the stored number when the stored
number has a positive polarity, but it must decrease the magnitude
of the stored number when that number has a negative polarity.
Similarly, a number decrementing signal, or signal that decreases
the actual value of the stored number, must decrease the magnitude
of that number when the stored number has a positive polarity, but
it must increase the magnitude of that number when the stored
number has a negative polarity.
Conventional multimode counting devices include a storage register,
means for transmitting number changing signals to the storage
register, and means for switching the operation of the counting
device from one mode to another. The storage register is
constructed to provide an output indicating the value of the stored
number. When the value of the stored number is zero, the storage
register provides an output that enables the mode switching means
to respond to the next number changing signal received by the
counting device and change the operating mode of the device
accordingly. If this next received number changing signal is a
number incrementing signal, the stored number will have a positive
polarity, and the mode determining apparatus provides an output
that will cause the counting device to operate in a first mode for
changing positive polarity numbers. Similarly, if this next
received number changing signal is a number decrementing signal,
the stored number will have a negative polarity and the mode
determining apparatus provides an output that will cause the
counting device to operate in a second mode for changing negative
polarity numbers.
In designing a counting and number storing device, it is desirable
to maximize the rate at which the device can receive number
changing signals. The rate at which signals can be received by the
above-described device is limited by the fact that a first signal
must propagate to the storage register, the value of the number
stored in the storage register must be changed in response to this
received number changing signal, the storage register must produce
an output indicating the value of the stored number, and this
output must propagate to and enable or activate the mode switching
means, before a second number changing signal can be received by
the counting and number storing device. If signals are received at
a faster rate, the mode determining means would not be ready to
respond to the signal received by the counting device immediately
following the number changing signal that causes the value of the
stored number to be zero and an error will occur.
SUMMARY OF THE INVENTION
The subject invention comprises a counting and number storing
device that can receive number changing signals at a faster rate
than can the prior art counters because it is constructed to
produce a signal that enables mode determining means to switch the
mode of operation at a time when it is known that the stored number
will have a zero value, but before that zero value is actually
obtained. In addition to mode determining means, the device
includes number storing means, means for receiving number changing
signals and transmitting those signals to the number storing means,
and means for providing a count direction signal that indicates
whether a number changing signal in transmission to the number
storing means will cause the magnitude of the stored number to be
incremented or decremented.
The number storing means includes gating means responsive to the
value of the stored number and the count direction signals for
providing an output signal that enables the mode determining means
to change the operating mode of the counting and number storing
device. The gating means is also connected to receive number
changing signals in transmission to the number storing means. An
enabling signal output is provided when the gating means receives
signals indicating that the magnitude of the stored number is unity
and that the next number changing signal to be received by the
number storing means will decrement the magnitude of the stored
number. This enabling signal allows the mode determining means to
receive and respond to the next number changing signal received by
the counting and number storing device. Since the number changing
signal that will cause the magnitude of the stored number to be
zero is the signal that caused the enabling signal to be
transmitted to the mode determining means, this next number
changing signal received by the device will be the signal that will
change the magnitude of the stored number from zero to either plus
or minus unity. The mode determining means receives and responds to
this signal, and provides an output that will cause the device to
operate in a first mode for changing a positive polarity number if
it is a number incrementing signal, and provides an output that
will cause the device to operate in a second mode for changing a
negative polarity number if it is a number decrementing signal.
Since an enabling signal is provided to the mode determining means
before the value of the stored number reaches zero, number changing
signals can be received by the counting device of this invention at
a faster rate than they can be received by the prior art counting
devices. There is no need for a first number changing signal to be
received by the number storing means and change the value of that
stored number before a second number changing signal can be
received by the subject counting and number storing device. It is
only necessary to determine that a number changing signal has been
received by the counting and number storing device that will cause
the stored number to have a zero value when the number storing
means of this device receive and respond to that signal.
To insure that the number changing signal received and used by the
enabled mode determining means to determine the operating mode of
the counting device is actually the number changing signal that
will change the value of the stored number from zero, the gating
means for transmitting an enabling signal to the mode determining
means is connected to receive number changing signals being
transmitted to the number storing means at a point downstream from
the point at which the mode determining means receives those
signals. The gating means is constructed to provide an enabling
signal only when the number changing signal that will cause the
stored number to have a zero value passes this downstream position.
This prevents the premature transmission of an enabling signal to
the mode determining means that would allow the mode determining
means to receive the number changing signal that will cause the
stored number to have a zero value instead of the number changing
signal that will cause the stored number to change from zero to
either plus or minus unity.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects, features and advantages of this invention, which
is defined by the appended claims, will become apparent from a
consideration of the following description, and the accompanying
drawing in which:
The FIGURE is a circuit diagram of one embodiment of the multimode
counting and number storing device in this invention.
DETAILED DESCRIPTION OF THE DRAWING
The FIGURE illustrates a multimode counting and number storing
device 10 that includes number storing means 12, means 14 for
receiving number changing signals and for transmitting those
signals to the number storing means 12, and means 16 for
determining the operating mode of the device 10. The device 10 also
includes gating and storing means 18 that provide count direction
signals that indicate whether each number changing signal in
transmission to the number storing means 12 will increment or
decrement the magnitude of the stored number.
The number storing means 12 includes four conventional decade
storage registers 20, 22, 24, and 26. Each register is constructed
to store a decimal digit of value 0-9 in a binary code form. Each
register includes a terminal labelled "CK" for receiving signals
hereinafter referred to as clock signals. The value of the digit
stored in a register is changed by each clock signal received by
that register. All clock signals transmitted to the registers 20-26
are identical. The direction in which a stored digit is changed is
determined by a count direction signal transmitted to the storage
registers along line 28 and received by those registers at
terminals labelled "MC". Gating and storing means 18 provides
either a first or a second count direction signal, depending on the
nature of the number changing signal received by the device 10 and
the polarity of the stored number. A first count direction signal
will cause the value of the stored digit to be increased by the
next received clock signal. A second count direction signal will
cause the number stored by a decimal register to be decreased upon
the receipt of the next clock signal. It is a characteristic of the
decade registers 20-26 that a count direction signal must be
received a predetermined amount of time before a clock signal in
order to qualify those registers to respond to the clock signal in
a proper manner.
Registers 20, 22, 24, and 26 stored progressively more significant
digits. That is, the least significant digit is stored in register
20, which is thus constructed to receive each clock signal
transmitted to the storing means 12. Signals transmitted along line
30 to the storing means 12 are placed in proper form for reception
by register 20 by an inverter 32. Registers 22, 24, and 26 do not
receive every clock signal transmitted to the number storing
apparatus since they store more significant digits. AND gates 34,
36, and 38 control the transmission of a clock signal to these
registers. Each of these AND gates will transmit a signal to its
associated decade register only upon the receipt of a clock signal
and signals from the terminals labelled "U/D" of each register
storing a less significant digit.
Each register includes gating means responsive to the value of the
stored digit and to the count direction signals for controlling the
transmission of signals from the "U/D" terminal. An output signal
is provided from the "U/D" terminal of a register only when the
digit 9 is stored in that register and a count direction signal is
received that will cause the next clock signal to increment the
value of the stored number, and when the digit 0 is stored in that
register and a count direction signal is received that will cause
the next clock signal to decrement the value of the stored
number.
A gate such as gate 36 controlling the transmission of clock
signals to the register 24 will transmit a clock signal to that
register only upon the receipt of a clock signal and output signals
from the "U/D" terminal registers 20 and 22. This insures that a
clock signal will change only the appropriate digits of a stored
number. For example, suppose the magnitude of the stored number
were 2,798 with the digits 2, 7, 9, and 8 stored in the registers
26, 24, 22, and 20, respectively. The receipt of a count direction
signal directing the magnitude of the stored number to be increased
and a clock signal would change only the digit in register 20 and
change the magnitude of the stored number to 2,799. However, the
receipt of another count direction signal directing the magnitude
of the stored number to be increased would cause registers 20 and
22 to provide output signals from their "U/D" terminals and qualify
gates 34 and 36, respectively, so that the next clock signal would
change the digits stored in registers 20, 22, and 24 to give the
stored number a magnitude of 2,800. Similarly, if the stored number
had a magnitude of 1,901, and a count direction signal directing
the magnitude of the stored number to be decreased were received,
the next clock signal would change only the value of the digit in
register 20 to give the stored number a magnitude of 1,900.
However, another signal directing the magnitude to be decreased
would cause registers 20 and 22 to provide output signals from
their "U/D" terminals to gates 34 and 36 so that the next clock
signal would change the digits stored in registers 20, 22, and 24
and give the stored number a magnitude of 1,899.
In addition to qualifying gates 34-38, the output signals from the
"U/D" terminals of decimal registers 22, 24, and 26 are transmitted
to a gating means 40 along lines 42, 44, and 46, respectively. The
binary signals representing the digits stored in register 20 are
transmitted to a One Detector 50 which is a known gating device
responsive to the binary code of the stored digit and designed to
provide an output signal along line 48 only when the digit stored
in register 20 has a magnitude of unity. Gating means 40 thus
receives signals along lines 42, 44, 46, and 48 when the magnitude
of the stored number is unity and a count direction signal has been
received by the storage registers 20, 22, 24, and 26 that directs
those registers to decrease the magnitude of the stored number in
response to the next received clock signal. Gating means 40
provides an output along line 52 only when signals are received on
lines 42, 44, 46, 48, and 54, but no signal is received along line
56. The receipt of a signal along line 54 and lack os a signal
along line 56 indicates that a clock signal is in transmission to
the decimal storage registers and that it has passed a
predetermined point 58 in its travel to those registers. Gating
means 40 thus provides an output signal when it is determined that
a clock signal is in transmission to the storage registers 20-46
that will cause the magnitude of the stored number to be zero, but
before the stored number actually obtains that zero value.
The output signal from gating means 40 is transmitted to a
flip-flop 60 which also receives clock signals along line 62.
Flip-flop 60 provides an output that enables the mode determining
apparatus 16 to respond to number changing signals received by the
device 10 and change the mode of operation of that device if
appropriate.
It is noted that gating means 40 could also provide an output
signal along line 52 when the stored number has a magnitude of 9991
and a count direction signal that directs the magnitude of the
stored number be increased by the next clock signal is received by
the registers 20-26. But since this value is at the extreme of the
count range, it can be considered an illegal state and ignored. It
would be an obvious matter for one skilled in this art to design
count registers in which the "U/D" terminals of the illustrated
registers are replaced by two output terminals, a first for
providing signals which qualify gates controlling the transmission
of clock signals to registers containing more significant digits,
and a second for providing output signals to gating means 40. An
output signal would be transmitted from this second terminal only
when the magnitude of the stored digit is zero and a count
direction signal is received that directs the magnitude of the
stored digit to be decremented by the next received clock signal.
This modified design would thus eliminate the transmission of an
erroneous signal from gating means 40 when the magnitude of the
stored number reaches 9991. However, it would only extend the range
of the counting device to 9999. Since this range extension is so
slight, the illustrated decade storage registers are used in the
preferred embodiment of this invention because they are
commercially available and can be obtained at less cost than can
the above-described modified registers.
The mode determining apparatus 16 receives number changing signals
from lines 64 and 66 of the receiving and transmitting apparatus
14, and responds to these signals upon the receipt of an
appropriate enabling signal from flip-flop 60. As has been
described above, a signal is transmitted to the mode determining
means 16 which enables those means to respond to the first number
changing signal received by the device 10 after it receives a
number changing signal that will cause the stored number to have a
value of zero. This signal following the zero causing signal will
cause the value of the stored number to have a value of either plus
or minus unity. If it is a number incrementing signal which will
give the stored number a positive polarity, the mode determining
means responds to this signal by providing an output to gating
means 18 that will cause the device 10 to operate in a first mode
for changing a positive polarity number. Similarly, if the number
changing signal following the zero causing signal is a number
decrementing signal which will thus give the stored number a
negative polarity, mode determining means 16 provides an output to
gating means 18 that causes the device 10 to operate in a second
mode for changing a negative polarity number.
In order to provide operation in the proper mode, AND gate 68
produces an output only upon receipt of a number changing signal
and an enabling signal from flip-flop 60. AND gate 68 provides a
high output along line 70 and a low output along line 72 upon
receipt of a signal from flip-flop 60 and a number incrementing
signal. It provides a low output along line 70 and a high output
along line 72 upon receipt of a signal from flip-flop 60 and a
number decrementing signal. The outputs from AND gate 68 are
transmitted to a sign flip-flop 74. This flip-flop provides a high
output along line 76 and a low output along line 78 in response to
the receipt of a high output along line 70. It will continue to
provide these outputs along lines 76 and 78 until a high signal is
received along line 72 and a low signal is received along line 70,
whereupon it will provide a low output along line 76 and high
output along line 78. This output state will also be maintained by
flip-flop 74 until further signals switching its output state are
received.
The signals transmitted along lines 76 and 78 determine the nature
of the count direction signal produced by gating means 18. Gating
means 18 is constructed to provide first count direction signals
that cause the magnitude of the stored number to be incremented,
and second count direction signals that cause the magnitude of the
stored number to be decremented. The particular output signal
provided by gating means 18 is determined by the number changing
and count direction signals received by gating means 18. Gating
means 18 stores received signals, provides an output determined by
the signals received, and continues to provide that output until it
receives either a subsequent count direction signal or a subsequent
number changing signal that will cause the output of gating means
18 to be changed. When gating means 18 receives a high signal along
line 76, it provides a first count direction signal in response to
each number incrementing signal it receives and a second count
direction signal in response to each number decrementing signal it
receives. A high signal received along line 76 thus causes gating
means 18 to operate in a first mode for changing the magnitude of a
positive polarity number. When gating means 18 receives a high
signal along line 78, it is constructed to provide a second count
direction signal in response to each number incrementing signal it
receives and a first count direction signal in response to each
number decrementing signal it receives. A high signal transmitted
along line 78 thus causes the gating means to operate in a second
mode for changing the magnitude of a negative polarity number.
Number incrementing and number decrementing signals are received by
the counting and number storing device 10 along lines 64 and 66,
respectively. These signals are received by the transmitting
apparatus 14 which generates a clock signal for each received
number incrementing and number decrementing signal. The receiving
and transmitting apparatus 14 includes delays 80 and 82 for
receiving number incrementing and number decrementing signals,
respectively. These delay devices delay the transmission of number
changing signals to the gating means 18 sufficiently so that the
mode determining means 16 will have time to receive each number
changing signal and change the operating mode of the device 10 in
the appropriate case before the number changing signal causing the
mode shift is received by the gating means 18. Delays 80 and 82
thus prevent the production of an erroneous count direction
indicating signal for the number changing signal that causes the
device 10 to shift from one mode of operation to another. Signals
from the delay device 80 and 82 are transmitted to an OR gate 84.
OR gate 84 provides an output signal upon receipt of a signal from
either delay 80 or delay 82. The output signals from OR gate 84 are
all identical and will be referred to hereinafter as clock signals.
The clock signal generated for a number incrementing signal is
indistinguishable from that generated for a number decrementing
signal.
Clock signals are transmitted from OR gate 84 to delays 86 and 88.
In combination, these delays delay the transmission of a clock
signal to allow sufficient time for the storage registers 20-26 to
receive and respond to the count direction signal associated with
the clock signal being delayed so that the clock signal will change
the magnitude of the stored number in the appropriate direction
upon receipt of the delayed clock signal. Delays 86 and 88 also
delay the transmission of a clock signal sufficiently so that
gating means 40 will receive a clock signal along line 56 and the
signals from the registers 20 to 26 that indicate the state the
storage registers will have upon receipt of that clock signal at
substantially the same time. This insures that no clock signal
other than the signal that will actually cause the stored number to
have a value of unity can qualify gating means 40 and cause the
transmission of an enabling signal to the mode determining means
16.
In order to prevent a long number changing signal from providing an
enabling signal and then gating itself rather than the next
following number changing signal into the mode determining means,
it is necessary to determine that the zero causing clock signal has
propagated past the point at which the mode determining means 16
receives number changing signals, before transmitting an enabling
signal to those mode determining means. Gating means 40 thus only
provides an output signal along line 52 when a clock signal is
received along line 54, but no signal is received along line 56.
Delay 88 separates the leading and trailing edges of a clock signal
so that a signal will be received by gating means 40 along line 56
for a sufficient time during which no signal is received along line
54 to allow gating means 40 to respond to that condition.
In operation, the counting and number storing device 10 receives
number incrementing and number decrementing signals along lines 64
and 66 respectively. The receiving and transmitting apparatus 14
produces an identical clock signal for each received number
changing signal. Each number changing signal is transmitted to the
gating means 18 which produces a count direction signal in
accordance with the nature of the number changing signal and the
polarity of the stored number. A count direction signal determines
whether its associated clock signal will increment or decrement the
magnitude of the stored number. Both the count direction signal and
its associated clock signal are transmitted to the number storing
means 12. The clock signal is delayed in transmission to allow
sufficient time for the number storing means 12 to receive and
respond to the count direction signal so that the magnitude of the
stored number will be changed in the appropriate direction by the
clock signal.
Gating means 40 provides an output when it is determined that the
stored number has a magnitude of unity and a clock signal is in
transmission to the storage registers 20-26 of the number storing
means 12 that will cause the stored number to be zero. That is,
storage registers 20-26 provide signal outputs to the gating means
40 along lines 42-48 when the magnitude of the stored number is
unity, and when a count direction signal is received that will
cause the registers to decrement the magnitude of the stored number
upon receipt of the next clock signal. Gating means 40 also
receives clock signals being transmitted to the number storing
means 12. The transmission of clock signals to gating means 40 is
delayed sufficiently so that the clock signal to be next received
by the storage registers 20-26 is received by the gating means 40
along line 54 at substantially the same time that gating means 40
receives signals indicating the magnitude of the stored number and
the direction the magnitude will be changed by the next received
clock signal. Gating means 40 provide an output signal along line
52 when signals are received along lines 42-48 and 54, and no
signal is received along line 56.
The clock signal that will cause the stored number to have a value
of zero causes gating means 40 to provide an output signal that
enables the mode determining means 16 to respond to the next number
changing signal received by the device 10. This next signal is the
signal that will change the value of the stored number from zero to
either plus or minus unity. This signal, therefore, determines the
polarity of the stored number and the operating mode of the device
10. To provide a change in the operating mode, the output from
gating means 40 is transmitted to flip-flop 60 which transmits an
enabling signal to AND gate 68 upon receipt of this signal and a
clock signal along line 62. AND gate 68 in cooperation with
flip-flop 74 determines the operating mode of the device 10. AND
gate 68 provides an output only in response to the receipt of both
a number changing signal and an enabling signal from flip-flop 60.
Number changing signals can, therefore, be received by the device
10 at a rate selected so that an enabling signal produced by one
number changing signal will be received by AND gate 68 at
substantially the same time that that gate receives the next number
changing signal.
The counting and number storing device thus is capable of receiving
number changing signals at a faster rate than prior art devices
because a first number changing signal need not be received by the
storage registers 20-26 and change the magnitude of the stored
number before the second number can be received by the counting
device as is the case with the prior art devices. A first signal
need only propagate past point 58 before a second number changing
signal can be received by the counting and number storing device
10, and no error in sign will be able to occur.
* * * * *