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This invention relates to a power management and automation system, and
more particularly, to such a system for managing the power consumption of
selective appliances and controlling the operation of such appliances in a
single facility, such as the home.
Energy management and home automation has been known for many years.
However, practical systems at reasonable cost, permitting effective energy
usage control and functionally controlling the operation of various home
appliances, still have not been developed. To the extent that such energy
control and automation systems have been developed, the homeowner becomes
a slave to the automatic system, rather than the automatic system being an
aide to the homeowner. For example, systems exist to automatically turn on
the lights at a certain time and turn them off at a second certain time.
However, in some situations, the homeowner may desire that the lights be
off when the computer has been set to keep them on. In such a situation,
the homeowner must reprogram the computer, rather than merely turn the
lights off by simply flipping a switch.
Examples of typical prior art automation and energy management systems are
shown in U.S. Pat. No. 4,740,882 in the name of Miller, U.S. Pat. No.
4,695,880 in the name of Johnson et al, U.S. Pat. No. 4,684,920 in the
name of Reiter, U.S. Pat. No. 4,642,473 in the name of Bryant, U.S. Pat.
No. 4,611,295 in the name of Fowler, U.S. Pat. No. 4,540,984 in the name
of Waldman, U.S. Pat. No. 4,497,031 in the name of Froehling et al, U.S.
Pat. No. 4,471,232 in the name of Peddie et al, U.S. Pat. No. 4,454,509 in
the name of Burnnagel et al, U.S. Pat. No. 4,418,333 in the name of
Schwarzbach et al, U.S. Pat. No. 4,389,577 in the name of Anderson et al,
U.S. Pat. No. 4,354,120 in the name of Schonnack, U.S. Pat. No. 4,345,162
in the name of Hammer, U.S. Pat. No. 4,319,319 in the name of Wygant, U.S.
Pat. No. 4,264,960 in the name of Gurr, U.S. Pat. No. 4,244,022 in the
name of Kendall, U.S. Pat. No. 4,223,379 in the name of Simcoe, U.S. Pat.
No. 4,217,646 in the name of Caltagirone et al, U.S. Pat. No. 4,213,182 in
the name of Eichelberger et al, U.S. Pat. No. 4,022,555 in the name of
Smith, U.S. Pat. No. 3,906,242 in the name of Stevenson and U.S. Pat. No.
3,790,815 in the name of Karklys. Other energy managements systems are
described in PCT Patent Application Number PCT/US 87/02365, entitled
"Energy Management System" in the name of Brown III et al and PCT Patent
Application Number PCT/US 87/02366, entitled "Responder For Energy
Management System" in the name of Brown, Jr. et al, and French Patent No.
2,495,396 in the name of Pillebout.
It is also well known that each electrical power circuit in a building,
such as a home, factory or the like, are protected by a fuse device, such
as a circuit breaker, against power surges and overloads. Many appliances
to be monitored, such as pumps and major appliances are included as the
only power consuming appliance in the circuit, that is, the circuit
breaker is designed to protect only that appliance. Other types of
appliances, such as lights, small kitchen appliances and the like, may be
grouped together in a single power circuit and share a common circuit
breaker.
Where circuit breakers are used to protect the power circuit, the circuit
breakers may include a small electric motor, which responds to appropriate
electric control signals for automatically tripping, setting or resetting
the circuit breaker from a remote location. One significant difference
between those appliances included with their own circuit breaker and those
appliances which must share a circuit breaker is that normally those
appliances having their own circuit breaker are almost universally subject
to automation and energy management, whereas only certain of the
appliances plugged in to a multi appliance circuit will be energy managed
and subject to automation. The motorized circuit breaker has been used in
the past as a convenient element to manage the application of power to
those single appliance circuits. Such motorized circuit breakers can be
turned off at those desired times when it is desired that they not
operate, such as the middle of the night for water heaters.
In order to have a fully automated facility, many times it is desirable for
external signals, indicating a certain status, to be provided to the
automation equipment in order to determine whether an appliance or device
should be turned on or off. For example, if an automatic sprinkler system
pump is being controlled by the automation system, it is desirable that
the system know whether the grass needs to be watered. Moisture sensing
transducers or rain gauge transducers are well known and can provide such
a signal indicating whether the ground is already moist or whether an
adequate amount of rain has fallen. If such signals are provided, the
automation system should respond thereto by not turning on the sprinkler
system. Another example is an automatic light control system which may
automatically turn on the lights at a certain time, such as dusk, and turn
off the lights at a certain other time, such as dawn. Optical sensors are
well known devices to control such outdoor lights. In some circumstances,
the homeowner desires to be able to override the sensor of the automation
system. Many prior art devices would require the homeowner to reprogram a
computer system, rather than simply operate a switch to reverse the
automation systems sensor commands.
The automation system may additionally include items which are not
typically subject to energy management such as being turned on and off.
For example, the automation system may include a security system which
responds upon sensing the opening or closing of windows or doors or the
detection of a person by motion or heat sensing equipment. Upon detecting
a breach of security, the automation system should automatically call for
assistance or sound an alarm. Such a system can be incorporated into an
overall automation system to automatically be turned on during certain
hours, such as the middle of the night or the normal daylight hours when
all family members are working or in school. However such security systems
must be easily reset whenever a family schedule change occurs, such as a
person arriving home late in the evening or staying home from work due to
illness, vacation, holidays and the like. Such resetting must be as simple
as existing free standing systems by operating an encoded switch or the
like, and not by reprogramming a computer.
In many energy management and home automation systems, it is not practical
in every instance to send the status signals determining whether
automation should occur or the homeowner override signals back to the
central automation computer. For one thing, a computer would become
overburdened in monitoring so many signals and this would result in delays
between the sending of a signal and the servicing of a signal. For
example, when the computer polling or being interrupted by a plurality of
a status or override signals becomes backlogged by servicing too many
requests, a person could walk into a room and find the lights would not go
on for several seconds after the switch was turned, the police would be
called before the security system override code was recognized and acted
upon by the computer. To solve this problem, some mechanism, which is
independent of the automation computer must be developed to override the
computer's commands. In addition, it is further necessary that the
homeowner have the final determination of whether the status signals are
to be followed. For example, despite the fact a status signal indicates
that sufficient rain has fallen so as to prevent the turning on of the
automatic sprinkler system, the homeowner may desire the system be turned
on for other reasons, such as newly planted grass. Hence, overall override
means must be provided under the control of the homeowner to override
either the automation system, as determined first by the computer system
or, second, as determined by the response to the status signals.
In accordance with one aspect of this invention, there is provided a power
management and automation system for controlling the operation of a
plurality of appliances in a facility. A first type of the controlled
appliances are the sole appliances in a first power circuit and a second
type of the controlled appliances are included with a plurality of
appliances grouped together in a second power circuit. Each power circuit
further includes a circuit breaker for controlling the application of
power to that power circuit. The system comprises a programmable
controller for providing a series of signals manifesting when operational
control of selected ones of either type of appliance is to occur. Further
the system includes a circuit breaker control module for providing an
output signal to control a switchable circuit breaker between the on and
off states so as to control the application of power to a selected first
type of appliance in the power circuit with which that switchable circuit
breaker is included and a point of use control module for providing an
output signal to a controllable switch means to control the application of
power to a selected one of the second type of appliances. Each of the
circuit breaker control modules and the point of use control modules
include manually operable switchable means associated therewith and an
input terminal to which is applied an externally provided control signal
from means associated with the appliance being operationally controlled
and processor means responsive to the programmable controller signals to
the operation of the manual operable switchable means and to the
externally provided signal for providing the output signal.
One preferred embodiment of the subject invention is hereafter described,
with specific reference being made to the following Figures, in which:
FIG. 1 shows the arrangement of a circuit breaker panel and the computer
automation and energy managing panel of the subject invention;
FIG. 2 is a side view of one of the control modules shown in FIG. 1;
FIG. 3 is a front view of the control module shown in FIG. 2;
FIG. 4 is an electrical block diagram of the system of the subject
invention; and
FIG. 5 is a block diagram of the internal circuitry of the breaker control
module or point of use module shown, in FIGS. 2 and 3;
Referring now to FIG. 1, automation and energy management panel 10 is shown
and may be positioned adjacent to a conventional circuit breaker panel 12.
Both of panels 10 and 12 may include an encloser, such as model number Q
040-M200 Manufactured by the Square D Company of Palatine, Illinois. Each
panel further would include a backplane (not shown) to which a module,
such as circuit breakers 14 or module 16, are snap locked for being held
in the panel boxes 10 or 12. The circuit breakers 14 may include manual
circuit breakers 14 and motorized circuit breakers 14M. Motorized circuit
breakers 14M may be controlled by signals applied to a small electric
actuated motor included therein to automatically be switchable between the
on and the off states. Both circuit breakers 14 and motorized circuit
breakers 14M are commonly available for various amperage ratings in the
marketplace, such as from the Square D Company.
It is well known that a circuit breaker, such as circuit breakers 14 or
14M, protect a single electric wiring circuit in a facility, such as the
home from overloads and power surges. The protected circuit may have a
single appliance or device associated therewith, such as a motor, water
heater or the like, or may have a plurality of different appliances, such
as lights and various small appliances connected through receptacles to
the circuit. Whenever a circuit breaker 14 or 14M is in the on position,
power may be applied to any or all of the appliances in that particular
power circuit and when the circuit breaker 14 or 14M is moved to the off
position, whether as a result of an overload or power surge, or as a
result of a signal applied to a motorized circuit breaker 14M or as a
result of a person manually tripping the breaker, power is disconnected
from that particular power circuit.
The automation and energy management panel 10 includes three principle
types of modules inserted therein. These modules are the power module 16,
the circuit breaker control module 18 and the device control module 20.
Each automation and energy management panel 10 will include one power
module 16, which is designed to provide power to the remaining modules.
Any number, within the space limitations of panel 10 of circuit breaker
control modules 18 or device control modules 20, may be inserted into
panel 10 depending on the number of motorized circuit breakers 14M or
individual devices to be controlled. Further, and as described hereafter,
each of the circuit breaker control modules 18 and device control modules
20 may be designed to control up to eight different motorized circuit
breakers 14M or individual devices.
Within panel 10, a backplane (not shown) is included and each of the
modules 16, 18 and 20 are snap locked to the backplane. In addition, a
wiring bus 22 is provided along the backplane and includes a plurality of
multi-pin connectors 24 into which each of the modules 16, 18 and 20 are
connected. Each of the connectors 24 may be hard wired with a different
address to permit a computerized facility controller 28, described in more
detail hereafter, to communicate therewith. To avoid confusion, the power
module 16 is always inserted into the top, or first, connector 24 and the
control modules 18 and 20 are inserted in any order into the next
successive lower connectors 24. The ends of wiring bus 22 each include a
pair of connectors 26, such as conventional RJ 11 telephone jacks, which
may be used to couple wiring bus 22 to a facility controller 28 or to a
second panel, similar to panel 10, containing additional circuit breaker
and device control modules 18 and 20.
Power module 16 receives 24 volt a.c. power from a power transformer 30,
which steps down the normal line current of 120 volts a.c. or 277 volts
a.c. to 24 volts a.c. The power module 16 regulated the a.c. signal
provided thereto and provides a 24 volt d.c. and a pair of 5 volt d.c.
signals over wiring bus 22 to the various modules 18 and 20 plugged into
connectors 24 of wiring bus 22. The two 5 volt d.c. signals provided by
power module 16 are applied to different ones of the circuit breaker
control modules 18 and device control modules 20 in order to prevent undue
loading on the 5 volt d.c. signal. The front of power module 16 includes
three light emitting diodes (LEDs) which, when illuminated, indicate that
the proper power is being applied from power module 16.
The circuit breaker control module 18 and device control module 20 are
identical, except for the type of output signal applied therefrom. The
output signal from circuit breaker control module 18 is designed to
actuate the motor included in one of the motorized circuit breakers 14M
contained in panel 12. Such actuation may be from the off to the on state
or from the on to the off state as desired. Typically, this signal is a
short pulse of, for instance, 75 milliseconds. The output signals from
device control module 20 may be pulses or steady state digital signals
designed to control other remote devices by, for example, permitting the
application of power thereto or preventing the application of power
thereto or causing a certain function to be performed. The other remote
devices may have motors which can be actuated to turn a switch from one to
another position, or may have relays which are maintained open or closed.
Alternatively, the remote device controlled by device control module 20
may, itself, be computer controlled by its own internal computer or by
facility controller 28, and would merely be looking for a change of state
of the signal provided thereto from module 20 and respond thereto in an
appropriate programmed manner. For example, an automatic telephone dialing
system may dial an emergency number, such as 911, in response to a signal
from module 20 going from a low to a high state.
Each of the modules 18 and 20 are also capable of receiving signals from
external sources in addition to the signals received over bus 22 from
facility controller 28. The external sources may be the device being
controlled or a sensor associated with the device being controlled. For
example, once an automatic telephone dialing system dialed the 911 number,
it could send an acknowledgment signal back to control module 20.
Alternatively, event signals could be sent to modules 18 or 20 to override
preprogrammed commands from facility computer 28. For example, a lawn
sprinkler motor may be preprogrammed to turn on at a certain time and the
override status signal from a rain gauge may prevent such action if it
detects the lawn is sufficiently wet or if it is raining.
Lastly, each of the control modules 18 and 20 include an override button 44
and status light 44 for each of the motorized circuit breakers 14M or
devices being controlled. The override buttons 42 may be actuated by a
person to override all other commands from facility controller 28 or from
the external signals and the status lights, by being on, off or flashing,
indicate the then existing status of the control function.
Referring now to FIGS. 2 and 3, the physical characteristics of control
modules 18 and 20 is shown, with FIG. 2 showing a side view and FIG. 3
showing a facing or front view of one of the modules 18 or 20. Each of the
modules 18 and 20 include a pair of clips 32 designed and positioned to be
snap locked into a conventional backplane used with panel 10. In addition,
a male connector 34 extends from the bottom of modules 18 or 20 and is
adapted to be plugged into one of the module female connectors 24, shown
in FIG. 1. When connector 34 is inserted into connector 24, both power
from power module 16, as well as control signals from facility controller
28 may be provided to the circuit elements contained on printed circuit
board 36 contained within module 18 or 20. Also connected to circuit board
36, is twenty-four output terminals 38 and sixteen input terminals 40,
each of which is adapted to having a single wire secured thereto. The
sixteen input terminals 40 may be grouped into eight pairs to provide a
pair of wires from each external source, such as the device being
controlled by one of the modules 18 or 20. Similarly, the output modules
contained eight groups of three terminals, so as to permit three wires to
be provided to each of the motorized circuit breaker 14M or devices being
controlled. Where a motorized circuit breaker 14M is being controlled, the
three wires of each group may be designated as a motor forward, a motor
reverse, and a common wire. Where an individual device is being
controlled, the three output terminals of each group may be designated as
a normally open contact, a normally closed contact and a common wire.
Eight manual override switch buttons 42 and eight status light emitting
diodes (LEDs) 44 are provided on the face of modules 18 and 20. Switches
42 may be depressed by the user, such as homeowner, of the automation and
energy management system to override any command signals, such as the
external signals from the devices being controlled or the command signals
from facility controller 28. The LEDs 44 may be illuminated, not
illuminated or flashing, possibility at several different rates, to
provide various status indication of whether one of the devices being
controlled is on or off, or the type of control then occurring.
The power module 16 is identical to the modules 18 and 20 shown in FIG. 2,
with the exception that output terminals 38 and input terminals 40 are not
present and the front panel only includes three light emitting diodes,
respectively representing the two plus five volt d.c. signals and the plus
24 volt d.c. signals provided by power module 16.
Referring now to FIG. 4, an electrical block diagram illustrating an
automation and energy management system 46 is shown. System 46 may, for
example, be a single home in which certain devices are managed for energy
usage and certain other devices are automated. In FIG. 4, elements
previously described are given like numerical designations. The heart of
system 46 is the facility controller 28. Facility controller 28 may be a
conventional personal computer, such as an I.B.M. personal computer XT, or
compatible or a specially modified computer device adapted specifically
for the automation and energy management function described herein.
Controller 28 will typically have a keyboard 48 and display 50 attached
thereto in a conventional manner for permitting the entrance of data
through the keyboard 48 or the display of messages to the user through
display 50. Controller 28 may additionally have other devices attached
thereto, such as memories, modems, printers and the like commonly found
with personal computers, or it may have specially adapted devices attached
thereto, such as security systems, video control systems, telephone
systems and the like.
Facility controller 28 provides the control signals to a data bus 52, which
is coupled, through connector 26 in FIG. 1, to be a part of wiring bus 22
in panel 10. The signals provided by controller 28 to data bus 52 will
typically identify the address of a particular one of the modules 18 or 20
and, within that addressed module, which one of the eight circuit breakers
or devices is to be controlled. The address of each module 18 or 20 is
determined by the address code pre-wired in the connector 24, as
previously discussed. Additionally, the facility controller 28 signal will
manifest a data code, such as indicating whether a switch should be turned
on or off.
As previously mentioned, power module 16 responds to a 16 volt a.c. signal
provided thereto from transformer 30, which, in turn, responds to the line
voltage, typically is 120 volts a.c. in a home. Power module 16 converts
the a.c. signal to three d.c. signals (+5 volts, +5 volts and +24 volts)
by using conventional voltage regulator circuit packs and these three d.c.
signals are provided from power module 16 to power bus 54. In addition,
power module 16 provides 8 volt a.c. and 24 volt a.c. signals, together
with d.c. and a.c. ground signals to power bus 54.
As previously described, both circuit breaker control module 18 and device
control module 20 have eight reset switch buttons 42 and eight status
lights 44 interconnected therewith. Further, each of modules 18 and 20
provide eight sets of output signals over connectors 38 and receive eight
sets of input signals through connectors 40. Specifically, with respect to
circuit breaker control module 18, up to eight motorized circuit breakers
14M may be coupled to the output connectors 38 as previously described.
Appropriate signals provided from module 18 can cause the motor associated
with any one of the motorized circuit breakers 14M to be force to the on
(closed) or off (open) condition. Module 18, thus, is typically used to
control devices which are the only devices within a particular power
circuit within the facility. For example, motors, water heaters, and the
like normally are wired as the only energy consuming device in a power
circuit, which of course, contains a circuit breaker. By making the
circuit breaker of such power circuits a motorized circuit breaker 14M,
the operation of such appliance itself may be easily controlled by simply
controlling the motorized circuit breaker 14M. Since control panel 10 may
be placed near circuit breaker panel 12, wiring is minimized between the
circuit breaker control module 18 and the motorized circuit breaker 14M,
as compared to providing wires to, for example, a remote relay of a
remotely switch controlled lights located outside the home.
Each power circuit protected by a motorized circuit breaker 14M provides
power to one of the controlled circuit device 56a through 56n. As
previously mentioned, the controlled circuit devices 56a through 56n, may
be hot water heaters, motors, for example used for sprinkling the lawn or
filtering a swimming pool, and the like. Each of these devices 56a through
56n may have a sensor either associated therewith, such as a thermostat,
in the case of the water heater, or a sensor located remote therefrom,
such as the moisture sensor or rain gauge associated with a lawn
sprinkling pump. Some, but not necessarily all, of the sensors 58a through
58n provide status signals to connector 40 to breaker control module 18.
For example, sensor 58b may be a thermostat associated with an hot water
heater device 56b which turns heating element in device 56b on and off
based upon its setting relative to the temperature of the water. Depending
upon the degree of automation desired, it may be unnecessary for
thermostat sensor 56b to provide its signal to breaker module 18. In this
case, no signals are applied to the terminal connectors of terminal 40
with respect to the second device being controlled 56b. Other sensors,
such as 58n, may be located remote from the device being controlled 56n,
such as a moisture sensor which is used to determine whether or not a
sprinkler pump should be turned on. Other sensors, such as a photo cell
associated with outside lights may be physically connected to the device
under control as indicated by sensor 58a associated with device 56a and
which provides a signal directly to module 18.
Device control module 20 is similar to circuit breaker control module 18,
except that the signals provided through output terminals 38 are provided
directly to the controlled individual devices 60a through 60n. Selected
ones of the controlled unit 60a through 60n also have a sensor 62a through
62n associated therewith in the same manner as sensors 58a through 58n
were associated with controlled circuit units 56a through 56n. In other
words, some sensors may be totally remote, others may be physically
connected with the device under control and still other units 60a through
60n under control may have no sensor. Again, signals are provided through
the output terminals 38 to control the various controlled individual
devices 60a through 60n, that is, to turn them on or turn them off or to
cause them to perform a particular function. The sensors 62a through 62n
may indicate, for example, whether the sensor is on or off or whether it
should be turned on or off or may constitute an acknowledgment that the
commanded function has been performed. The sensors 62a through 62n may
also indicate a manual command, such as an override, by the homeowner. In
other words, if one of the controlled individual units 60 is a motorized
light switch for a room, the sensor 62 associated with that unit could be
an indication of whether the homeowner has physically turned the switch on
or off. In this case, that would override whatever the facility controller
28 instructed module 20 to do with respect to that device.
In addition to the principle circuit breaker control module 18 and device
control module 20, shown in system 46, other modules 64, which may or may
not include reset buttons 42 or status lights 44, may be inserted into
panel 10. Such other modules may be used to control security or to control
certain specialized appliances, such as video tape recorders and the like.
Generally, the other modules 64 will operate on other devices 66 and
receive status signals from other input 68. They may also provide signals
to the other inputs/outputs devices 68 to control them, as well as receive
status signals therefrom. While the other modules are shown in system 46
as receiving signals from facility controller 28, this may or may not be
the case in that they may be totally independent of facility controller 28
or may be coupled thereto only to provide status information rather than
to receive control.
Referring now to FIG. 5, a block diagram of the electronic system 70 within
one of the modules 18 or 20 is shown. Components previously described are
given the prior identification numbers. The heart of system 70 is an eight
bit microprocessor, which includes internal random access memory (RAM),
such as the Motorola microprocessor number 63705. Microprocessor 72 is
under the control of a program contained in the EPROM 74, that determines
the functions microprocessor 72 performs. These functions may be varied
depending on the setting of jumpers 76 associated with microprocessor 72.
Microprocessor 72 operates under the control of a 4.9152 MHz crystal
oscillator clock 78. Synchronization is maintained by the 60 hertz timing
reference and wave shaping circuit 80, which synchronizes microprocessor
72 with the other similar microprocessors within the other modules 18 or
20. Such synchronization is necessary because facility controller 28 only
communicates with one module 18 or 20 at a time over bus 52. Thus, the
various microprocessors similar to 72 and the other modules are merely
waiting for access to bus 52 and must be synchronized based on a common
stable frequency.
The watchdog timer circuit 82 is an internal supervisor and monitor for
microprocessor 72. Microprocessor 72 periodically sends acknowledgment
signals to watchdog timer circuit 82 to indicate that it is properly
functioning without any disturbances. If these acknowledgments signals are
too late or too early, watchdog circuit 82 is connected to reset processor
72 and restart it.
Communication between microprocessor 72 and facility controller 28, shown
in FIG. 4, is over bus 52. This is controlled by the address detect
circuit 84 and the bus interface circuit 86. As previously mentioned, the
address of each module 18 or 20 is hard wired into connector 24; when an
appropriate address is provided over bus 52, the address detector 84
detects that address based on the hard wired connector 24 and permits
microprocessor 72 to have access to bus 52 by opening bus interface
circuit 86.
Each of the input lines connected to input terminal 40 are provided through
an input protection circuit 88. Microprocessor 70 continually monitors the
signals provided to input protection circuit 88 and notes any change
therein requiring a change in the output signals. Some status signal
changes will result in immediate action by microprocessor 74 and others
will be stored in the internal RAM to inhibit action in response to
commands from facility controller 28. Similarly, the status lights 44 are
in communication with microprocessor 70 through a status circuit 90 and
the reset buttons 42 are in communication through a reset circuit 92.
Microprocessor 72 is programmed to provide signals to illuminate the
various status lights 44 or check whether a light is on or off through
status circuit 90. Similarly, microprocessor 72 monitors communication
with the reset buttons 42 through reset circuit 92 in that it can send
signals to the buttons or receive signals whenever one of the buttons 42
is depressed.
The output signals provided over terminals 38 are provided through output
drivers 94. Again, output drivers 94 are coupled to be in two way
communication with microprocessor 72 in that microprocessor 72 can provide
signals through output driver circuit 94 to any one or more of the 24
output terminals or it can read the signal on any of the output terminals.
The type of driver circuits included in output driver circuit 94 will
depend upon whether a motorized circuit breaker 14M or a device 60a-60n
is being controlled. This circuit is the only one which will differ
between the circuit breaker control module 18 and the device control
module 20.
As is apparent from FIG. 5, microprocessor 72 may be controlled from three
different sources. These three sources would be the facility controller
28, the status signals provided through input protection circuit 88 and
the manual operation of one of the reset buttons 42. Under some
circumstances, microprocessor 72 could receive conflicting information
from the three different inputs thereto. Thus, an order of prioritization
is required and this order has been selected to be such that the highest
priority is the push buttons 42, the next highest priority is the status
signals applied through the input terminals 40 and the lowest priority | | |
