Note: Descriptions are shown in the official language in which they were submitted.
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HVAC EQUIPMENT PHASE AND VOLTAGE MONITOR AND CONTROL
TECHNICAL FIELD
This application is directed, in general, to a
heating, ventilation and air conditioning (HVAC) and, more
specifically, to power and control of HVAC systems.
BACKGROUND
Modern HVAC systems typically employ three-phase
power from a'local transmission line to operate. HVAC units
are often manufactured to be installed to buildings with a
variety of voltages and frequencies. Various components of
a system may include a compressor or a fan motor. When such
components are three-phase components, e.g., configured to
operate using all three phases of the available line power,
the condition of the voltage supplied by each phase of the
line power is critical to the operation of the system. When
one or more phases of the line power falls outside an
allowable range, or is crossed with another phase, three-
phase components may not operate correctly or may be damaged
by continued operation. Damaging power conditions can
occur, e.g., due to improper installation, service and
electrical supply.
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SUMMARY
One embodiment, as described herein, provides an
HVAC unit having a transformer and a system controller.
The transformer is configured to receive power from a
first and a second phase of a three-phase power source
and to produce a first reduced-voltage waveform
therefrom. The system controller is adapted to sample the
reduced voltage waveform to determine a figure of merit
of the three-phase power source. The system controller is
further configured to operate the HVAC unit in response
to the figure of merit.
Another aspect provides a method of manufacturing an
HVAC system. The method includes configuring an HVAC unit
and a system controller. The HVAC unit is configured to
receive an input power source and reduce a voltage of the
input power source to a reduced voltage. The system
controller of the HVAC unit is adapted to sample the
reduced voltage to quantify a figure of merit of the
input line voltage. The system controller is configured
to operate the HVAC unit in response to the figure of
merit.
Yet another aspect provides an HVAC power protection
system, including a keyed connector block, a keyed
connector, and a controller subsystem. The keyed
connector block is configured to receive three power
phases from a three-phase power source. The keyed
connector is configured to mechanically couple to the
keyed connector block and thereby electrically couple a
first transformer to a first phase and a second phase of
the three-phase power source. The controller subsystem is
configured to receive a first reduced-voltage waveform
derived from an output of the first transformer and
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sample the first reduced-voltage waveform with an analog to
digital converter. A microcontroller is configured to
receive a converted voltage from the analog to digital
converter and quantify a figure of merit of the three-phase
power source. The microcontrolier is further configured to
operate the HVAC unit in response to the figure of merit.
In one aspect, there is provided an HVAC unit,
comprising:
a first transformer configured to receive power from
a first and a second phase of a three-phase power source
and to produce a first voltage waveform therefrom;
a second transformer configured to receive power from
said first and a third phase of said three-phase power
source and to produce a second reduced-voltage waveform
therefrom; and
a system controller adapted to sample said voltage
waveform to determine a figure of merit of said three-phase
power source, said system controller being further
configured to operate said HVAC unit in response to said
figure of merit.
In one aspect, there is provided a method of
manufacturing an HVAC system, the method comprising:
configuring an HVAC unit to receive three-phase power;
adapting a system controller of said HVAC unit to
derive a first waveform from a first phase and a second
phase of said three-phase power;
derive a second waveform from said first and a third
phase of said three-phase power;
quantify a figure of merit based on said first and
second waveforms; and
configuring said system controller to operate said
HVAC unit in response to said figure of merit.
In one aspect, there is provided an HVAC power
protection system, comprising:
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a keyed connector block configured to receive three
power phases from a three-phase power source;
a keyed connector configured to mechanically couple
to said keyed connector block and to electrically couple a
first transformer to a first phase and a second phase of
said three-phase power source;
a controller subsystem configured to receive a first
voltage waveform derived from an output of said first
transformer and sample said first voltage waveform with an
analog to digital converter; and
a microcontroller configured to receive a converted
voltage from said analog to digital converter and quantify
therefrom a figure of merit of said three-phase power
source, said microcontroller being further configured to
operate an HVAC unit in response to said figure of merit.
BRIEF DESCRIPTION
Reference is now made to the following descriptions
taken in conjunction with the accompanying drawings, in
which:
FIG. 1 illustrates an HVAC system of the disclosure
connected to a three-phase power source;
FIG. 2 illustrates a keyed connector and connector
block;
FIG. 3 illustrates phase relationships of three-phase
power lines;
FIG. 4 illustrates half-wave rectification of step-
down transformer outputs and a sampling and
characterization subsystem of the disclosure;
FIGs. 5 and 7 illustrate sampled half-wave waveforms
and figures of merit associated therewith; and
FIG. 6 is one embodiment of a method covered by the
disclosure.
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DETAILED DESCRIPTION
The present disclosure benefits from the unique
recognition that the likelihood of power-related
malfunction or damage in an HVAC system may be substantially
reduced by an integrated approach to line power
distribution and monitoring. The approach includes keyed
power connectors and connector blocks to reduce the
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chance of mis-wiring within the HVAC system, and
quantifying one or more key figures of merit to quickly
make a control decision in response to a line condition
excursion.
Conventional three-phase HVAC power monitors are
typically limited to phase characterization input line
voltage. Moreover, such a monitor may require additional
hardware when the power source to which it is connected
provides the line voltage at a higher value than the
monitor is designed to accommodate. The limited
characterization provided by such modules provides at
best an incomplete picture of the status of the input
power. Moreover, the response of such a monitor to a
phase error is typically limited to disabling the
associated HVAC system via a cutoff relay. Thus, there is
no means to assess the risk of a power supply excursion
and control the HVAC system accordingly.
Turning initially to FIG. 1, illustrated is an
embodiment of the disclosure of an HVAC system, generally
designated 100. The HVAC system 100 includes a compressor
110, a fan motor 120 and a system controller 130. The
system 100 is a nonlimiting example illustrative of
various HVAC systems including without limitation indoor
units, outdoor units, and heat pumps. Three-phase power
lines 140 provide power to the HVAC system 100. The power
lines 140 are referred to for convenience as LI, L2, and
L3. Herein, one or more of the power lines 140 may be
referred to simply as a "phase" of the three-phase power
lines 140. Various components of the HVAC system 100 may
be configured to operate using one or more phases of the
three-phase power lines 140.
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The power lines 140 are illustrated as providing
power from a utility pole 150, but the disclosure is not
limited to such embodiments. For example, power may be
provided by a portable power generation system or locally
produced power such as photovoltaics.
When one or more of the lines LI, L2, L3 experience a
voltage or phase excursion, or two or more of the lines
are switched, components of the HVAC system 100 such as
the compressor 110 and the fan motor 120 may cease to
operate properly, or may be damaged. For instance, an
under-voltage condition on L2 may cause an increased load
on L1 and L3 windings of the compressor 110 or the fan
motor 120, with damage resulting if these components are
operated too long with the under-voltage condition. The
compressor 110 and/or fan motor 120 may also be damaged
by operating while an over-voltage condition exists.
Similarly, for example, the compressor 110 and/or the fan
motor 120 may be damaged or rendered inoperable if L1 and
L2 are switched. In some cases, the HVAC system 100 may
include components that operate using single phase power
derived from a local transformer. In these cases, such
damage may still be caused by over-and under-voltage
conditions.
The lines 1,1, L2, L3 are illustrated as entering a
connector block 160. Connectors 161, 162, 163 may be used
to distribute power to the various components of the
system 100, including, as illustrated, the compressor
110, the fan motor 120 and the system controller 130. As
mentioned, in many cases it is desirable, and may be
essential, that LI, L2f and L3 be provided to the various
components in the correct order. To reduce the
possibility that Ll, L2 or L3 will be mis-wired internally
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to the system 100, the connector block 160 and connectors
161, 162, 163 may be keyed to ensure a desired connector
polarity is preserved.
FIG. 2 illustrates an embodiment of the connector
block 160 and the connector 162 without limitation. The
connector block 160 includes receptacles 210, and the
connector 162 includes pins 220. A space D1 between the
receptacles 210 associated with Li and L2 is smaller than
a space D2 between the receptacles 210 associated with L2
and L3. Similarly, a space D1' between the pins 220
associated with L1 and L2 is smaller than a space D2'
between the pins 220 associated with L2 and L3. The
spacing between the receptacles 210 and the pins 220 is
matched, e.g., D1= D1' and D2= D2'. Thus when the connector
162 is mated to the connector block 160 the ordering of
L2 and L3 is guaranteed to be preserved at the
junction between the connector block 160 and the
connector 162. Thus, the connector block 160 and the
connector 162 are keyed to each other. Of course, proper
hookup to the connector block 160 and the connector 162
is still needed to ensure that Ll, L2 and L3 reach the fan
motor 120 in the proper order.
Incorrect connections to the connector block 160, or
to the connectors 161, 162, 163 may still result in
incorrect ordering of Li, L2 and L3 at the system 100
components. Advantageously, the disclosure provides in
various embodiments for the detection of incorrect
phasing of 1,1, L2 and L3, as well as characteristics of
various figures of merit including, e.g., voltage, phase
and frequency excursions.
Turning briefly to FIG. 3, the phase relationships
between Ll, L2 and L3 are illustrated. Ll, having a phase
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(pi, may be arbitrarily assigned a phase of 0 radians or 0
degrees. A phase 02 of L2 follows COI, having a relative
phase of about -5- radians, or about -120 degrees. A
3
phase 03 of L3 follows 02, having a phase relative to 0=
about - ______ radians, or about -240 degrees. The order of
3
the phases of 1,1, L2 and L3 may be represented as 123123_.
However, because the assignment of 0 radian phase is
arbitrary, the phase order may be equivalently viewed as
123_, 231_ or 312_. These permutations of Ll, L2 and L3
are referred to herein as operable permutations. Various
embodiments described herein may detect all of these
operable permutations. Furthermore, as described below,
various embodiments may detect any permutations of 1,1, L2
and L3 that are not operable permutations. If a
permutation other that those in the operable set is
detected, the HVAC system 100 may be prevented from
operating until the error is corrected. Thus, various
components of the HVAC system 100 are protected from
damage that may result from operation with an
impermissible permutation of 1,1, L2 and L3.
Turning to FIG. 4, illustrated is an embodiment of
the disclosure of the system controller 130. Transformers
410, 420 receive the three-phase power lines 1,1, L2 and
L3. The power lines 1,1, L2, L3 typically carry a voltage of
208 VAC or greater to power various high-load HVAC
devices such as the compressor 110. The voltage carried
by the lines 1,1, L2, L3 typically has a frequency of 50 Hz
or 60 Hz, depending on the standard used by the utility
providing the power. One or more transformers such as the
transformers 410, 420 may be used to reduce, or step
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down, the voltage from the line voltage to a voltage
compatible with control electronics associated with the
system controller 130. For the purpose of discussion,
without limitation the output voltage of the transformers
410, 420 is taken to be 24 VAC RMS. (Hereinafter all AC
voltages are taken to be root-mean-square voltages unless
expressly stated otherwise.) The transformer design may
be different for different line voltage levels. For
example, a transformer designed to step down 230 VAC to
24 VAC will typically have a different design than a
transformer designed to reduce 460 VAC to 24 VAC.
One node of the primary coil of the transformer 410
is coupled to the L1 line input, and the other node of the
primary coil is coupled to the L2 line input. A reduced-
voltage output voltage 430 has a same frequency as the
line inputs 1,1, L2. One node of the primary coil of the
transformer 420 is coupled to the L1 line input, and the
other node of the primary coil is coupled to the L3 line
input. A reduced-voltage output voltage 440 has a same
frequency as the line inputs 1,1, L3.
The output voltage 430 may be half-wave rectified by
a diode 450 to produce a half-wave waveform 470.
Similarly, the output voltage 440 may be half-wave
rectified by a diode 460 to produce a half-wave waveform
480. Both the half-wave waveform 470 and the half-wave
waveform 480 are also reduced-voltage waveforms. The
waveforms 470, 480 may be used, e.g., to power various
components of the HVAC system 100 such as control
electronics, either directly or after further voltage
conditioning such as capacitive filtering. The waveforms
470, 480 are characterized by a half-wave (positive)
modulation above zero volts, with a peak value of the
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waveform 470 leading a peak value of the waveform 480 by
about 1 of the period of the voltage provided via LI, L2
and L3, e.g., about radians or about 60 degrees.
The system controller 130 includes a sampling and
characterization subsystem 485. The subsystem 485 is
configured to sample the waveforms 470, 480 and quantify
figures of merit associated therewith, discussed below.
In the illustrated embodiment the subsystem 485 includes
an analog-to-digital converter (ADC) 490 and a
microcontroller 495. While illustrated as separate
components, the ADC 490 and the microcontroller 495 may
be integrated in a single packaged device in some
embodiments. The waveform 470 is input to a first input
of the ADC 490, and the waveform 480 is output to a
second input of the ADC 490. The ADC 490 is configured to
cooperate with the microcontroller 495 to provide
digitized samples of the waveforms 470, 480 thereto. The
ADC 490 may include additional components such as an
analog multiplexer to switch between the waveform 470 and
the waveform 480 during sampling.
The microcontroller 495 may be any programmable
state machine configurable to receive data from the ADC
490 and quantify therefrom figures of merit associated
with the waveforms 470, 480. In various embodiments the
microcontroller 495 is configured to execute instructions
stored in memory, e.g., a program. The microcontroller
495 may also control the aspects of the operation of the
ADC 490 to acquire samples of the waveforms 470, 480 at
specific times or rates. The instructions may include any
instructions to acquire and manipulate data, and to
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provide control outputs that may be used to control
various operational aspects of the system 100.
In some embodiments the microcontroller 495 is used
to control other aspects of the operation of the system
100, such as controlling the compressor 110 and the fan
motor 120, or communicating over the communication
network 170 with other HVAC components. However,
embodiments are contemplated in which the microcontroller
495 is dedicated to the collection and characterization
of data from the waveforms 470, 480.
In various embodiments the ADC 490 is configured to
sample the instantaneous magnitude of the waveforms 470,
480 to produce a digital representation of the
instantaneous values thereof. The sampled values may be
used by the microcontroller 495 to determine a
representation of the time-varying characteristics of the
waveforms 470, 480. The microcontroller 495 in various
embodiments is additionally configured to quantify
figures of merit associated with the waveforms 470, 480
that may be used as proxies for characteristics of the
power lines Ll, L2, L3.
FIG. 5 illustrates one embodiment of a sampling
scheme that may be carried out by the system controller
130. The waveform 470 is illustrated including two half-
waves 510 having a magnitude Mi and a period 14f, where f
is the frequency of the waveform 470. In a nonlimiting
example, the magnitude M1 is about 34 volts, corresponding
to the peak voltage of a 24 VAC sine wave. In another
nonlimiting example, the period 14f is about 16.7 ms,
equivalent to a line frequency of about 60 Hz. The ADC
490 acquires a first sample of the waveform 470 at a time
T1, and a second sample at a time T2. The time AT=T2-T1
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between the first and the second sample may be any
desired value, but in various embodiments AT is
advantageously selected to result in at least 10 samples
within the time span of the half-wave 510, e.g., about
20.r In applications requiring greater resolution of the
sampled waveform, AT may be selected to acquire a sample
at a rate at least about 40f.
The waveform 480 is also illustrated including two
half-waves, and has a magnitude M2. The waveform 480 may
be sampled at a same or different time than the waveform
470, and at a same or different rate that the waveform
470. In various embodiments the waveform 480 is sampled
after a small delay, e.g., a few microseconds, accounting
for the time it takes a calling routine to return the
sampled value of the waveform 470 and return to acquire a
sample of the waveform 480.
In addition to the magnitudes MI, M2 and the
frequency f, the waveforms 470, 480 may also be
characterized by a phase difference ATI as a figure of
merit. In the illustrated embodiment, a peak of the
waveform 480 lags a peak of the waveform 470 by 49. The
phase difference Ay) is also a phase difference of the
output voltage 440 relative to the output voltage 430
(FIG. 4). This case represents a proper ordering of the
phases of LI, L2 and L3, e.g., the ordering illustrated by
FIG. 2. The phase difference Lp in this case is a
consequence of the configuration of the transformers 410,
420, e.g., where L1 is coupled to a first terminal of each
transformer 410, 420, and L2 and L3 are respectively
coupled to a second terminal of each transformer 410,
420.
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An instruction program running on the
microcontroller 495 may perform post-acquisition
processing of the values sampled from the waveforms 470,
480 to quantify various figures of merit. Without
limitation, such figures of merit may include the voltage
magnitudes M1, M2, f, and the phase difference LT between
the waveform 470 and the waveform 480. Any other figure
of merit deemed to be useful in assessing the condition
of the three-phase power lines 140 is within the scope of
the disclosure. When desired, a figure of merit may be
converted to a figure of merit of the line inputs Ll, L2,
L3 using known deign parameters of the transformers 410,
420. The microcontroller 495 may then make various
control decisions based on the values obtained for the
desired figures of merit.
FIG. 6 illustrates an example embodiment of a method
600 configured to acquire digitized samples of the
waveforms 470, 480 and perform quantitative analysis
thereof. Those skilled in the pertinent art will
recognize that the method 600 is one of many methods that
may yield equivalent functionality of the system
controller 130. Such equivalents are explicitly
contemplated by the disclosure.
The method 600 begins with an entry state 601, which
may be entered from any appropriate calling routine of an
instruction program. In a step 605, a sample value of the
waveform 470, represented as T1, is acquired. In a step
610, the acquired value is tested to determine if it is
nonzero. The test may include a noise threshold to
account for the presence of noise on the waveform 470. In
one embodiment, the noise threshold is 10% of the
expected value of M1, e.g. about 3.4 V. If the acquired
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value is zero, or within the range near zero treated as
zero, then the method 600 returns to the step 605, at
which another sample is acquired. Such a case is
represented by the samples at Tl and T2 in FIG. 5.
When the acquired sample exceeds the noise
threshold, as represented by the sample at T3 in FIG. 5,
then the method advances to a step 615. The value
acquired at T3 is referred to as a first nonzero value of
the waveform 470. In the step 615, a sample value of the
waveform 480, represented as (1)2, is acquired. In a step
620, if the value 92 is zero, the method progresses to a
step 625, discussed below. If the value y2 is nonzero, an
error condition is determined to have occurred, and the
method advances to an error handling state 660.
13 The error condition detected by the occurrence of a
nonzero value of p2 simultaneously with the first nonzero
value of 91 may be interpreted as improper phasing of at
least one of the line inputs LI, L2, L3. As described
previously, the phase difference A9 illustrated in FIG. 5
represents the case that the waveform 480 lags the
waveform 470. Such a case indicates that the line inputs
Ll, L2, 13 are properly ordered, e.g., 123, 231 or 312.
FIG. 7 illustrates the waveform 470 and the waveform
480 for the case that the line inputs 1,1, L2, L3 are
arranged in other than an allowable order, e.g., 213, 132
or 321. In each of these cases, the peak of the waveform
480 leads a peak of the waveform 470 by about 1- radians
or about 60 degrees. Thus, the first nonzero value of the
waveform 470 at the time T3 occurs when the value of the
waveform 480 is nonzero. This combination of acquired
values of the waveform 470 and the waveform 480 is a
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signature of improper ordering of the line inputs LI, 12,
L3.
Returning to FIG. 6, if the value of p2=0 in the
state 620, no error is deemed to have occurred and the
method advances to a step 625. In the step 625 the
waveforms 470, 480 are sampled for at least one period.
In some cases, the waveforms are sampled for a time
greater than a highest expected period to reduce any need
for a priori knowledge of the period of the line voltage
provided by the utility. The acquired data may be
buffered in memory for various post-acquisition
processing.
In a step 630, the frequency f of the line voltage
inputs is determined. In one embodiment, the period 1/f
between peaks of either the waveform 470 or the waveform
480 is determined, and the frequency computed therefrom.
In another embodiment, the period of both of the
waveforms 470, 480 is determined for confirmation of the
determined frequency, and to ensure that the
determination tests all three of the lines Ll, L2, L3. If
in a decisional step 635 the frequency is determined to
be within an allowable range, e.g., 5% of an expected
frequency, the method 600 advances to a step 640.
Otherwise the method 600 advances to the error handling
state 660.
In the step 640, the magnitude of at least one of
the waveforms 470, 480 is determined. In one embodiment,
the magnitude of both the waveforms 470, 480 is
determined. As described earlier, the magnitude is
expected to be about 34 V when the transformers 410, 420
provide 24 VAC. In an embodiment, Mi is used to compute
the line voltage of Ll, L2, L3 using known characteristics
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of the transformers 410, 420, and the computed value is
compared to an expected value. If in a decisional step
645 the magnitude of the waveform 470 and/or the waveform
480 is within an allowable range, e.g., 25% of an
expected value, then the method 600 advances to a step
650. If instead the magnitude of one or both of the
waveforms 470, 480 is not within the allowable range the
method proceeds to the error handling state 660.
In the step 650, the phase lag Ap between the
waveform 470 and the waveform 480 is determined. This
value may be computed from the measured time interval
between a peak of the waveform 470 and the next peak of
the waveform 480, and the period 1/f as determined by the
interval between one peak of the waveform 470 and the
next peak of the waveform 470. If in a decisional step
655 n9 is within an allowable range, e.g., 5% of an
expected value, then the method 600 advances to an exit
state 699. The expected value may be, e.g., about
radians or about 60 degrees. If instead Ap is not within
the allowable range the method proceeds to the error
handling state 660.
The method 600 may include comparing one or more of
the figures of merit, e.g., frequency, magnitude and
phase, to a stored configuration profile. Such a profile
may be stored by the system controller 130, and may
further be preconfigured by a manufacturer to include
values reflecting a particular configuration of the
system 100. For example, one configuration profile may
include an expected frequency value of 60 Hz for a system
intended for service in North America, while another
configuration profile may include an expected frequency
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value of 50 Hz for a system intended for service in
Europe. The configuration profile may be provided, e.g.,
by a pre-programmed nonvolatile memory installed by the
manufacturer when the destination of the system 100 is
determined.
In the error handling state 660, the method 600 may
include various responses to error conditions determined
from the various quantified figures of merit. The
response may be to disable the operation of the system
100 until the condition is cleared, and may include
recording the occurrence of the error and logging a time
and date. The response may include generating a warning
signal. The warning signal may include an audible
warning, a visual warning, or a message sent via the
network 170 to a listening device. A message may include
a message configured to alert an operator, installer, or
service provider of the error via email, MMS (multimedia
messaging service) or paging device. In some cases, such
as for minor or brief excursions of a figure of merit
from an allowable operating range, the system 100 may be
allowed to continue operating, while optionally
generating a warning signal and/or error message and
logging the event to memory.
The combination of keyed power connectors and
monitoring of the input power lines provides a unique and
highly applicable means of ensuring that proper power is
delivered to the system 100. The keyed power connectors
reduce the possibility of installation errors, either in
a manufacturing setting or in the field, and the power
monitoring provides visibility to errors connecting the
system 100 to the utility lines, or to voltage or phase
excursions in the power delivery system. In this manner,
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the possibility of damage to the system 100 is greatly
reduced relative to conventional HVAC systems and
operation, and user comfort and system reliability are
enhanced.
Those skilled in the art to which this application
relates will appreciate that other and further additions,
deletions, substitutions and modifications may be made to
the described embodiments.
