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Claims  |
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That which is claimed is:
1. A video security system, comprising:
a video monitor connected to receive a monitor video signal and for
displaying a video image represented by the monitor video signal;
a plurality of cameras each disposed at a location remote from said video
monitor for producing a camera video signal representing an image of the
respective remote location;
a first switching control unit for receiving configuration data and for
generating first switching control signals in accordance with the
configuration data;
a second switching control unit for receiving configuration data and for
generating second switching control signals in accordance with the
configuration data;
a video switching unit connected for receiving the camera video signal from
each of said plurality of cameras, for receiving the first switching
control signals, and for providing the monitor video signal to said video
monitor from among the camera video signals in accordance with the
received switching control signals;
configuration selection means for generating the configuration data, said
configuration selection means being connected for transmitting the
configuration data to said first switching control unit;
a backup controller connected with said configuration selection means for
monitoring the configuration data transmitted to said first switching
control unit and providing a duplicate of the configuration data to said
second switching control unit in tandem with the transmission of the
configuration data to said first switching control unit, said backup
controller further comprises detection means for detecting a failure
condition of said first switching control unit and for generating a
transfer control signal in response thereto; and
transfer means responsive to the transfer control signal for disconnecting
said configuration selection means from said first switching control unit
and connecting said configuration selection means to said second switching
control unit, wherein said video switching unit further for receiving the
second switching control signals generated by said second switching
control unit upon the detection of a failure condition by said backup
controller.
2. The security system of claim 1, wherein
said video switching unit comprises a first video switching unit for
receiving the first switching control signals;
said security system further comprising:
a second video switching unit connected for receiving the camera video
signals from each of said plurality of cameras, and for receiving the
second switching control signals, said second video switching unit being
adapted for providing the monitor video signal from among the camera video
signals in accordance with the second switching control signals; and still
further wherein
said transfer means is responsive to the transfer control signal for
disconnecting said first video switching unit from said video monitor and
for connecting said second video switching unit with said video monitor
for providing the video monitor signal thereto.
3. The security system of claim 1, further comprising
a power source operatively connected for providing electrical power to said
backup controller and said transfer means, and wherein
said transfer means further comprises switching means adapted for
maintaining a connection state among said configuration selection means,
said first switching control unit, and said second switching control unit
in the event of a failure of said power source.
4. The security system of claim 1, further wherein
said first switching control unit is programmed for acknowledging receipt
of the configuration data from said configuration selection means, and
wherein
said detection means is further adapted for detecting a failure of said
first switching control unit to acknowledge receipt of the configuration
data transmitted from said configuration selection means.
5. The security system of claim 4, still further wherein
said first switching control unit is further programmed to transmit a
status indicating signal, and
said detection means is further configured to detect an error in the status
indicating signal or an absence of the status indicating signal.
6. The security system of claim 1, further wherein said configuration
selection means comprises a general purpose computer.
7. The security system of claim 1, further wherein said configuration
selection means comprises a control console having a keyboard.
8. The security system of claim 1, further comprising
an alarm switch connected for providing an alarm signal to said backup
controller,
said backup controller further being adapted for transmitting the alarm
signal to corresponding alarm inputs of said first switching control unit
and said second switching control unit.
9. The security system of claim 1, further comprising
a signal distribution unit for providing camera control signals to said
plurality of cameras for operating said cameras, and
wherein the configuration data contains the camera control signals and said
backup controller is further adapted for transmitting the camera control
signals to said signal distribution unit.
10. The security system of claim 1, wherein
said backup controller further comprises a switch having a pole connected
to a data output port of said first switching control unit, a second pole
connected to a data output port of said second switching control unit, and
an output terminal, the switch being responsive to the transfer control
signal for disconnecting the output terminal from the first pole and
connecting the output terminal to the second pole.
11. A video security system, comprising:
a video monitor connected to receive a monitor video signal and for
displaying a video image represented by the monitor video signal;
a plurality of cameras each disposed at a location remote from said video
monitor for producing a camera video signal representing an image of the
respective remote location;
a first switching control unit for receiving configuration data and for
generating first switching control signals in accordance with the
configuration data;
a second switching control unit for receiving configuration data and for
generating second switching control signals in accordance with the
configuration data;
a first video switching unit connected to said first switching control unit
for receiving the first switching control signals, and operatively
connected for receiving the camera video signal from each of said
plurality of cameras and for providing the monitor video signal to said
video monitor from among the camera video signals in accordance with the
first switching control signals;
a second video switching unit connected to said second switching control
unit for receiving the second switching control signals, and operatively
connected for receiving the camera video signals from each of said
plurality of cameras, said second video switching unit being adapted for
providing the monitor video signal from among the camera video signals in
accordance with the second switching control signals;
configuration selection means for generating the configuration data, said
configuration selection means being connected for transmitting the
configuration data to said first switching control unit;
a backup controller connected with said configuration selection means for
monitoring the configuration data transmitted to said first switching
control unit and providing a duplicate of the configuration data to said
second switching control unit in tandem with the transmission of the
configuration data to said first switching control unit, said backup
controller further comprises detection means for detecting a failure
condition of said first switching control unit and for activating a
transfer control signal in response thereto; and
transfer means responsive to said transfer control signal for (i)
disconnecting said configuration selection means from said first switching
control unit and connecting said configuration selection means to said
second video switching control unit and (ii) disconnecting said first
video switching unit from said monitor and connecting said second video
switching unit to said monitor.
12. The security system of claim 11, further comprising
a power source operatively connected for providing electrical power to said
backup controller and said transfer means, and wherein
said transfer means further comprises switching means adapted for
maintaining a connection state among said configuration selection means,
said first switching control unit, and said second switching control unit
in the event of a failure of said power source.
13. The security system of claim 11, wherein
said first switching control unit is programmed for acknowledging receipt
of the configuration data from said configuration selection means, and
wherein
said detection means is further adapted for detecting a failure of said
first switching control unit to acknowledge receipt of the configuration
data transmitted from said configuration selection means.
14. The security system of claim 13, wherein
said first switching control unit is further programmed to transmit a
status indicating signal, and
said detection means is further configured to detect an error in the status
indicating signal or an absence of the status indicating signal.
15. The security system of claim 11, further wherein said configuration
selection means comprises a general purpose computer.
16. The security system of claim 11, further wherein said configuration
selection means comprises a control console having a keyboard.
17. The security system of claim 11, further comprising
an alarm switch connected for providing an alarm signal to said backup
controller,
said backup controller further being adapted for transmitting the alarm
signal to corresponding alarm inputs of said first switching control unit
and said second switching control unit.
18. The security system of claim 11, further comprising
a signal distribution unit for providing camera control signals to said
plurality of cameras for operating said cameras, and
wherein the configuration data contains the camera control signals and said
backup controller is further adapted for transmitting the camera control
signals to said signal distribution unit.
19. The security system of claim 11, wherein
said backup controller further comprises a switch having a first pole
connected to a data output port of said first switching control unit, a
second pole connected to a data output port of said second switching
control unit, and an output terminal, the switch being responsive to the
transfer control signal for disconnecting the output terminal from said
first pole and connecting the output terminal to said second pole.
20. A video security system, comprising:
a video monitor connected to receive a monitor video signal and for
displaying a video image represented by the monitor video signal;
a plurality of cameras each disposed at a location remote from said video
monitor for producing a camera video signal representing an image of the
respective remote location;
a first switching control unit for receiving configuration data and for
generating first switching control signals in accordance with the
configuration data;
a second switching control unit for receiving configuration data and for
generating second switching control signals in accordance with the
configuration data;
a first video switching unit connected to said first switching control unit
for receiving the first switching control signals, and operatively
connected for receiving the camera video signal from each of said
plurality of cameras and for providing the monitor video signal to said
video monitor from among the camera video signals in accordance with the
first switching control signals;
a second video switching unit connected to said second switching control
unit for receiving the second switching control signals, and operatively
connected for receiving the camera video signals from each of said
plurality of cameras, said second video switching unit being adapted for
providing the monitor video signal from among the camera video signals in
accordance with the second switching control signals;
configuration selection means for generating the configuration data, said
configuration selection means being connected for transmitting the
configuration data to a first input of said first switching control unit,
said configuration selection means further for allowing a system user to
specify a desired configuration in a manner which does not immediately
affect an operation of said first switching control unit, the desired
configuration corresponding to configuration data to be transmitted to the
first input of said first switching control unit, said configuration
selection means further being responsive to a system user command for
initiating the transmission of the configuration data to said first
switching control unit;
configuration-altering means for altering the configuration data during a
real-time operation of said security system, said configuration-altering
means being connected for transmitting the configuration data to a second
input of said first switching control unit, wherein the configuration data
includes configuration data as altered by said configuration-altering
means;
a backup controller connected with said configuration selection means and
said configuration-altering means for monitoring the configuration data
transmitted to said first switching control unit and providing a duplicate
of the configuration data to a first input and a second input of said
second switching control unit, respectively, in tandem with the
transmission of configuration data to the first input and the second input
of said first switching control unit, respectively, wherein the
configuration data received by said second switching control unit is
continuously maintained consistent with the configuration data in the
first switching control unit, said backup controller further comprises
detection means for detecting a failure condition of said first switching
control unit and for activating a transfer control signal in response
thereto; and
transfer means responsive to said transfer control signal for (i)
automatically disconnecting said configuration selection means and said
configuration-altering means from said first switching control unit and
connecting said configuration selection means and said
configuration-altering means to said second video switching control unit
and (ii) automatically disconnecting said first video switching unit from
said monitor and connecting said second video switching unit to said
monitor. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The present invention relates to a video security system and, in particular
to a video security system having redundant video matrix switching control
units and a backup control system for ensuring that data within a backup
video matrix switching control unit is identical to that stored in a main
video matrix switching control unit. The backup control system also
effects transfer of control of the video security system to the backup
switching control unit when a failure of the main unit is detected.
BACKGROUND OF THE INVENTION
Video security systems are widely employed in facilities where it is
desirable to monitor events at a number of locations within the facility.
Such security systems typically include a video matrix switching apparatus
which connects signals from a plurality of cameras to one or more video
monitors so that an operator at a single location can view activity in any
of the monitored locations. Typically, operation of the video matrix
switching apparatus is controlled in accordance with a program stored
within a switching control unit. Such a switching control unit may be
co-located with the matrix switching apparatus or, alternatively, the
switching control unit may be at a remote location from the switching
apparatus. It is often desirable to provide redundancy in such security
systems such as by installing multiple cameras at each monitored location
so that a failure of one camera does not result in a loss of the ability
to observe that location. A security system provided with redundant
peripheral equipment, such as cameras, monitors, and the like, is still
vulnerable to a total loss of ability to observe any of the monitored
locations if the video matrix switching apparatus or its associated
controller fails. It would be desirable to and is accordingly an object of
the present invention have a video security system wherein a backup video
matrix switching apparatus or a backup switching controller is
automatically substituted for a main video matrix switching apparatus or
main switching controller, respectively, in the event of a failure.
Ideally, the backup switching apparatus would be substantially similar to
the main unit in structure and function so that a transfer of operation
between the main and the backup units occurs in a manner that is
transparent to the operator. Additionally, it would be desirable and is
accordingly an object of the present invention to have a backup control
system that does not depend on any specialized backup control features of
the main unit, so that a previously installed video security system could
be equipped with backup capability without having to re-program or to
replace the existing video matrix switching apparatus or its associated
switching controller.
Video switching systems are known which are capable of providing complex
remote monitoring features in accordance with configuration data
maintained within the memory of the switching controller. Configuration
data such as switching sequences, video captions, alarm response routines,
and the like, can be specified and/or altered during operation of the
video security system. In order to provide transparent transfer of control
from such a switching control system to a backup switching control system,
it would be desirable and is accordingly an object of the present
invention to specify and/or alter similar configuration data within the
memory of the backup switching control system so that, at the time control
is transferred, the backup switching control system operates in accordance
with the same configuration data used by the main switching control system
just prior to the transfer.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a video security
system is provided having at least one video monitor connected to receive
a video signal and for displaying a video image represented by the video
signal; a plurality of cameras each disposed at a location remote from the
video monitor for producing a video signal representing an image of the
respective remote location; a first video switching unit connected for
receiving the video signal from each of the plurality of cameras and for
providing the video signal to the video monitor; and a first switching
control unit for receiving configuration data and for providing switching
control signals to the first switching unit in accordance with the
switching control signals. The video security system according to this
invention also includes a second switching control unit for receiving the
configuration data and for providing switching control signals to a second
video switching unit. The second video switching unit has a video output
terminal and is operable to provide the video signal to the output
terminal in accordance with the switching control signals received from
the second switching control unit. A configuration selector generates the
configuration data and is connected for transmitting the configuration
data to the first switching control unit. A backup controller connected
with the configuration selector monitors the configuration data
transmitted to the first switching control unit and provides a duplicate
of said configuration data to the second switching control unit. The
backup controller includes a detection means for detecting a failure
condition of the first switching control unit and produces a transfer
control signal in response thereto. A transfer mechanism is connected to
receive the transfer control signal and, in response thereto, disconnects
the video monitor from the first video switching unit, connects the video
monitor to the output terminal of the second video switching unit, and
transfers control of the video security system to the backup switching
control unit.
In an alternative embodiment of the present invention, a video security
system is provided having at least one video monitor connected to receive
a video signal and for displaying a video image represented by the video
signal; a plurality of cameras each disposed at a location remote from the
video monitor for producing a video signal representing an image of the
respective remote location; a first switching control unit for receiving
configuration data and for providing switching control signals; and a
video switching unit connected for (i) receiving the video signal from
each of the plurality of cameras, (ii) receiving the switching control
signals, and (iii) providing the video signal to the video monitor in
accordance with the switching control signals. The video security system
according to this invention also includes a second switching control unit
connected for receiving the configuration data. A configuration selector
generates the configuration data and is connected for transmitting the
configuration data to the video switching control unit. A backup
controller, connected with the configuration selector, monitors the
configuration data transmitted to the first switching control unit and
provides a duplicate of said configuration data to the second switching
control unit. The backup controller includes a detection means for
detecting a failure condition of the first switching control unit and
produces a transfer control signal in response thereto. A transfer
mechanism is connected to receive the transfer control signal and, in
response thereto, disconnects the video switching unit from the first
switching control unit and then connects it with the second switching
control unit, thereby transferring control of the video security system to
the second switching control unit when a failure of the first switching
control unit is detected.
According to another aspect of the present invention, a backup controller
for a video security system is adapted for duplicating configuration data
provided to a main switching control unit and for transmitting the
duplicated data to a backup switching control unit during operation of the
video security system. Thus, the backup controller ensures that
configuration data maintained in the memory of the backup switching
control unit is essentially the same as that maintained in the main
switching control unit. In the course of monitoring communications made to
the main switching control unit from any peripheral equipment capable of
altering the configuration data, the backup controller also monitors the
response of the main switching control unit to such communications in
order to detect any failure of the main switching control unit to properly
respond. Upon detection of a failure of the main switching control unit to
respond, the backup controller transfers control of the video security
system to the backup switching control unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary as well as the following detailed description of the
preferred embodiments of the present invention will be better understood
when read in conjunction with the appended drawings, in which:
FIG. 1 is a diagram of a known video security system;
FIG. 2 is a diagram of a video security system in accordance with the
present invention;
FIG. 3 is a partial schematic of the interconnections of peripheral
equipment, the main video switching unit, and the backup video switching
unit to and through the backup controller of the video security system
shown in FIG. 2; and
FIG. 4 is a diagram of a video security system in accordance with an
alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown a known surveillance system 10. The
surveillance system 10 includes one or more video cameras, 12a, 12b, and
12c that are each at a remote location to be monitored. Each of the video
cameras produces a video signal that is transmitted to an input terminal,
designated VIDEO IN, of a centrally located video matrix switching unit
17.
The VIDEO IN terminal of the switching unit 17 includes a plurality of
coaxial connectors for receiving video signals from the cameras 12a-c.
Other sources of video signals, such as video outputs from other switching
units, may be connected to the VIDEO IN terminal of the switching unit 17.
The switching unit 17 also has a VIDEO OUT terminal which preferably
includes a plurality of connectors for attaching one or more monitors
16a-c to the switching unit 17. The switching unit 17 is operative to
provide any of the VIDEO IN signals to any of the monitors 16a-c in
response to switching control signals provided by a switching control unit
14.
The switching control unit 14 executes a sequencing program that controls
the connections made by the switching unit 17 between input video signals
and the video output terminals, VIDEO OUT, so that any or all of the
monitors 16a-c will display a selected image or sequence of images
corresponding to selected video input signals.
The switching unit 17 and the switching control unit 14 are housed within
an enclosure 19, such as a "card cage" or equipment rack, providing a
communication bus (not shown) there in for transmitting switching control
signals from the switching control unit 14 to the switching unit 17.
Electrical power is provided to the switching unit 17 and the switching
control unit 14 from a power supply 13. Such combined switcher/controller
systems are commercially-available as the TC8X00 family of
microprocessor-based matrix switcher/controller systems manufactured by
Burle Industries, Inc. of Lancaster, Pa.
The sequence by which input video signals are connected to the video output
terminals is determined according to configuration data stored in a memory
within the switching control unit 14. The configuration data includes
sequence parameters that define one or more switching sequences. The
switching control unit 14 is adapted for storing several different sets of
sequence parameters that can be retrieved from the memory and utilized
selectively, in accordance with prevailing circumstances, to cause a
desired sequence of images to be displayed upon any of the monitors 16a-c.
The switching control unit 14 preferably includes an auxiliary
communication terminal, COM2, to permit communication with additional
peripheral equipment or with a remote switching unit or units. The
switching unit 17 is also equipped to provide video output signals to
video recording equipment or to another switching unit or units in a
distributed video surveillance network.
The switching control unit 14 includes a keyboard terminal KB, to which a
keyboard 18 is connected. The keyboard 18 includes a plurality of keys, a
display, and a joystick. By "keying in" parameters, the system operator
provides control information to the switching control unit 14 in response
to prompts shown on the keyboard display. For example, the operator can
specify the sequence parameters according to which the video input signals
will be connected to the video output terminals of the switching unit 17.
The keyboard is provided with a joystick or similar device so that the user
can pan and/or tilt a camera. Such a camera control arrangement is
described in greater detail in commonly owned, copending application Ser.
No. 08/263,782, now U.S. Pat. No. 5,517,236. Briefly, camera control
commands are entered by the user through the keyboard 18. The switching
control unit 14 interprets the entered commands or joystick movements and
then issues a camera control signal, via the CAM terminal, to a signal
distribution unit (SDU) 20. The signal distribution unit 20 then
broadcasts the control signal to the cameras 12a-c via a camera control
signal distribution network 22. The cameras are operative to receive
control signals from the SDU 20 and to respond by adjusting their
position, focus, zoom, exposure, or other parameter as specified by the
user.
In an alternative embodiment, two or more keyboards are connected to the
switching control unit 14. For example, each of several keyboards may be
associated with one of several clusters of monitors so that multiple users
may each select the video signals to be displayed upon their respectively
assigned cluster of monitors. In such an embodiment, it is desirable to
define, for each user, a subset of the configuration data that each user
is permitted to alter. Various permission arrangements can be defined by a
designated master user in the form of a user access table that is stored
in the memory of the switching control unit 14. The user access table is
employed by the switching control unit 14 to determine such information as
which cameras, monitors, and/or sequences each user is permitted to use.
Additionally, each user is assigned a unique identification code and/or
password which must be entered whenever the user begins a surveillance
session.
In-order to actively alert a user to a potentially important event, the
surveillance system 10 includes a plurality of alarm switches 24 that are
connected with the ALARM terminal of the switching control unit 14. Such
alarm switches include, for example, intrusion detection devices in areas
monitored by the cameras 12a-c. Whenever the switching control unit 14
detects activation of one of the alarm switches, a predetermined response
is effected by the switching control unit 14 in accordance with
configuration data in an alarm table that is stored in the memory of the
switching control unit 14. For example, one entry in the alarm table
instructs the switching control unit 14 to cause the switching unit 17 to
display, on a selected monitor, the image from a specified camera in
response to the activation of a corresponding alarm switch. Another alarm
table entry instructs the switching control unit 14 to cause the switching
unit 17 to maintain a specified image upon a specified monitor for a
selected period of time, or until the user at a selected keyboard
acknowledges that an alarm event has occurred.
Additional configuration data stored in the memory of the switching control
unit 14, includes a time-event table whereby the switching control unit 14
is instructed to operate in accordance with particular configuration data
at specified times of the day, days of the week, or similar cyclic
intervals. For example, it may be desirable to operate the switching
control unit 14 in accordance with a first configuration during daytime
business hours, and in accordance with a second configuration during other
periods of time. In such an arrangement, a first alarm table for use
during the daytime causes the switching control unit 14 to ignore an alarm
switch located at an entryway, while at night, a second alarm table would
cause the switching control unit 14 to respond to activity at the entryway
by causing the switching unit 17 to select an appropriate video input
signal for display upon a selected monitor. The time-event table is used
by the switching control unit 14 to select alarm tables or sequence
parameters for use at specified times. Additionally, the time-event table
can be used to effect the execution of other specified functions at
specified times defined within the time-event table.
As can be appreciated, the switching control unit 14 is highly configurable
in that many aspects of its operation are selected and/or altered by the
operator during operation of the surveillance system 10. In a complex
installation utilizing a large quantity of customized configuration data,
the selection or alteration of such data by the user via the keyboard 18
is cumbersome and time-consuming. In such a system, it is preferable to
provide a computer 26 that is programmed to allow the user to specify,
edit, and/or store the configuration data. The computer 26 can be
programmed to allow the user to specify and/or edit the desired
configuration data "offline", i.e., in a manner that does not immediately
affect the operation of the switching control unit 14. A bi-directional
data link 28 connects the computer 26 to the COM1 terminal of the
switching control unit 14 so that configuration data can be downloaded
from the computer to the switching control unit 14. Additionally,
configuration data can be uploaded from the switching control unit 14 to
the computer 26 for editing.
During operation of the surveillance system 10, communication is maintained
between the computer 26 and the switching control unit 14 so that an
operator stationed at the computer 26 can obtain such information as the
status of any alarms, the identity of users logged on to any of the
keyboards, the sequences being displayed upon the monitors, and the like.
In the preferred embodiment, the computer 26 operates under the ALLEGIANT
Master Control Software, published by Burle Industries, Inc. of Lancaster,
Pa.
Uninterrupted operation of the surveillance system 10 depends entirely upon
uninterrupted operation of the switching control unit 14. The failure of
any single peripheral component of the surveillance system 10, such as a
camera, although potentially inconvenient, would not be catastrophic. In a
secure installation, sufficient redundancy can be provided so that
security is not compromised by the failure of any single component of the
surveillance system 10 of FIG. 1. However, the exception to that rule is
the switching control unit 14.
It would be desirable and is accordingly an object of the present invention
to substantially eliminate the possibility of a single-point failure of
the switching control unit 14, by providing a backup switching control
unit that would assume the functions of the main switching control unit in
the event of failure of the main unit. Because the switching control unit
14 contains and utilizes a considerable quantity of customized
configuration data which can be altered during operation of the system, it
is especially desirable and is accordingly an object of the present
invention to continuously update the configuration of the backup switching
control unit so that, in the event of failure of the main switching
control unit, the backup unit can assume all of the functions of the main
unit at any time.
Referring now to FIG. 2, there is shown a preferred embodiment of a video
security system 100 according to the present invention. The video security
system 100 has a main switching control unit 14' and a backup switching
control unit 34.
The main switching control unit 14' is operationally connected with a main
switching unit 17' both of which are mounted within an enclosure 19'.
During normal operation of the security system 100, the main switching
unit 17' receives video signals at its VIDEO IN terminal, and supplies
video output signals to the monitors 16a', 16b', and 16c' in response to
switching control signals from the main switching control unit 14' in
accordance with configuration data stored in the memory of the main
switching control unit 14'.
Operating in tandem with the main switching control unit 14' is a backup
switching control unit 34. The backup switching control unit 34 is
substantially identical in function and programming to the main switching
control unit 14'. The backup switching control unit 34 is operatively
connected therein with a backup switching unit 37, both of which are
preferably housed within an enclosure 35.
The main switching control unit 14' is supplied with electrical power from
power supply 13'. The backup switching control unit 34 is supplied with
electrical power from a separate power supply 15 that is preferably
independent of power supply 13'. During normal operation of the security
system 100, the backup switching control unit 34 and its associated
switching unit 37 receive the same inputs as the main switching control
unit 14' and its associated switching unit 17'. However, the backup units
are not connected to certain components of the security system 100 as
described more fully hereinbelow.
The security system 100 has a backup control system including transfer
relays 38, 40, and 42 and a backup controller 36. The relay 38 is
connected between the VIDEO OUT terminals of the main and backup switching
units and normally connects the main switching unit 17' with the monitors
16a' -16c'. The relay 40 is connected between the COM2 ports of the main
and backup units and normally connects the main switching control unit 14'
with an external status monitoring device (not shown). The relay 42 is
connected between the CAM ports of the main and backup units and normally
connects the main switching control unit with the camera control signal
distribution unit 20'.
The backup controller 36 is adapted to detect a malfunction of the main
switching control unit 14' and to then effect transfer of control of the
security system 100 to the backup switching control unit 34 by effecting
operation of the transfer relays 38, 40, and 42. When a failure of the
main switching control unit 14' is detected by the backup controller 36,
the backup controller 36 provides a transfer control signal, along signal
line 44 to the relays 38, 40, and 42, so that the relays operate to
connect the COM2, and CAM terminals of the backup switching control unit
34, and to connect the VIDEO OUT terminals of the backup switching unit,
with the appropriate peripheral devices.
As can be appreciated, the backup switching control unit 34 need not be
connected to certain peripheral equipment, such as the cameras 12a'-c',
during normal operation because the lack of connection to such devices
does not present a risk of losing consistency between the configuration
data stored in the memory of the backup switching control unit 34 and that
stored in the main switching control unit 14'. Other peripheral devices,
such as the keyboard 18', are used during normal operation to alter
configuration data within the main switching control unit 14'. Thus, the
control signals that are transmitted from such configuration-altering
peripheral devices should be provided to the backup switching control unit
34 in tandem with the transmission of those control signals to the main
switching control unit 14'.
In a preferred embodiment, the keyboard 18' is connected via bi-directional
link 60, to the backup controller 36. Control signals transmitted from the
keyboard 18' are duplicated by the backup controller 36 and transmitted to
the keyboard terminal KB of the main switching control unit 14' along
bi-directional link 64. The backup controller 36 replicates the keyboard
control signals and provides the replicated control signals to the
keyboard terminal KB of backup switching control unit 34 via link 72.
During normal operation of the main switching control unit 14', any signals
that are transmitted from the keyboard terminal KB of the main switching
unit 14' along link 64 are routed through the backup controller 36 to
keyboard 18' via link 60. However, any signals that are transmitted from
the keyboard terminal KB of the backup switching control unit 34 along
link 72 are not routed to the keyboard 18' via link 60. Instead, the
backup controller provides termination of the data transmission lines of
link 72 in the direction from the keyboard terminal KB of backup switching
control unit 34, so that the backup switching control unit 34 behaves as
if a keyboard were directly connected to its keyboard terminal. In other
words, the backup controller 36 maintains two-way communication between
the main switching control unit 14' and the keyboard 18', but only one-way
communication (i.e., from the keyboard 18' to the backup switching control
unit 34) is provided between the keyboard 18' and the backup switching
control unit 34. When the backup controller 36 detects a failure of main
switching control unit 14', the backup controller 36 severs the two-way
connection between the keyboard 18' and the main switching control unit
14'. The backup controller 36 then establishes two-way communication
between the keyboard 18' and the backup switching control unit 34.
Concurrent with the establishment of two-way communication between the
keyboard 18' and the backup switching control unit 34, the backup
controller transmits the transfer control signal over signal line 44 to
the relays 38, 40, and 42 to effect connection of the backup switching
control unit 34 and its associated switching unit 37 with other peripheral
equipment in the security system 100. In the preferred embodiment, the
relays 38, 40, and 42 and the other switching mechanisms of the backup
controller 36 are of a type that maintain the most-recently established
connection status in the event that the backup controller 36, and hence
the signal line 44, undergoes a loss of power. Thus, the backup controller
36 does not itself introduce any significant additional failure
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