U.S. patent number 3,789,384 [Application Number 05/319,445] was granted by the patent office on 1974-01-29 for security system operated by changes in light at specified locations.
This patent grant is currently assigned to Lawrence Security Inc.. Invention is credited to Artie E. Akers.
United States Patent |
3,789,384 |
Akers |
January 29, 1974 |
SECURITY SYSTEM OPERATED BY CHANGES IN LIGHT AT SPECIFIED
LOCATIONS
Abstract
A security system for the detection of moving targets such as
intruders and also of fire and explosions. A plurality of sensors
such as photoelectric cells or infrared detectors are focused in an
inner and outer pattern, such as pairs of nearly coaxial cones, of
different slope, for example, to create inner and outer zones of
intrusion. The outputs from the sensors are coupled through a
sequencing unit which is programmed to yield an output only when
intrusion into the inner zone follows intrusion into the outer zone
no more quickly than after a predetermined time delay. A fire
detection system places sensors in an area to be protected,
utilizing the same general type of operation as the intruder
protection with some differences. A plurality of lockout sensors
sensing ambient light conditions to lockout the sequencing units of
the intrusion detection system and fire detection system if the
changes are due to changes in the ambient light.
Inventors: |
Akers; Artie E. (Long Beach,
CA) |
Assignee: |
Lawrence Security Inc. (San
Francisco, CA)
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Family
ID: |
23242262 |
Appl.
No.: |
05/319,445 |
Filed: |
December 29, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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140808 |
May 6, 1971 |
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Current U.S.
Class: |
340/521; 340/523;
340/578; 250/221; 340/555 |
Current CPC
Class: |
G08B
13/19 (20130101); G08B 19/00 (20130101) |
Current International
Class: |
G08B
13/19 (20060101); G08B 19/00 (20060101); G08B
13/189 (20060101); G08b 013/00 () |
Field of
Search: |
;340/258B,276,420
;250/221 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Caldwell; John W.
Assistant Examiner: Mooney; Robert J.
Attorney, Agent or Firm: Owen, Wickersham & Erickson
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
140,808 filed May 6, 1971.
Claims
I claim:
1. A security system for the detection of moving targets
comprising:
a plurality of sensors focused in inner and outer patterns, the
said patterns creating inner and outer zones of intrustion;
a sequence unit having first and second inputs and an output, said
first and second inputs coupled to outputs of said sensors and said
sequence unit being operable for producing an output after an input
from said outer zone sensor and an input from said inner zone
sensor after a predetermined delay.
2. The security system of claim 1 and further including:
a lockout unit, said lockout unit having an input and an output
coupled to an inhibit input of said sequence unit; and
at least one lockout sensor disposed in proximity to said inner and
outer sensors for sensing ambient conditions surrounding said zones
of intrusion.
3. The security system of claim 1 and further including:
a circuit coupled to a first group of said inner and outer zone
sensors operable for yielding an output signal of one polarity;
and
a second group of sensors coupled to a second circuit means for
yielding an output of another polarity with an identical variation
in light condition within the inner and outer zones of
intrusion.
4. The security system of claim 1 wherein:
said inner and outer zones of intrusion comprise substantially
coaxial cones.
5. The security system of claim 1 and including:
first and second fire detecting sensors each having an output;
and
first and second threshold detectors having inputs coupled to the
outputs of first and second fire sensors, respectively, said first
and second threshold detectors being set for different levels of
detection.
6. The security system of claim 5 and further including:
a second sequence unit having first and second inputs coupled to
the outputs of said first and second threshold detectors, said
sequence unit being programmed for yielding an output after
receiving first and second inputs in a predetermined time sequence;
and
a second lockout means having an input coupled to at least one said
lockout sensor and an output coupled to an inhibit input of said
sequence unit.
7. A security system for detecting moving intruders, including in
combination:
an A-series of sensor means for detecting changes in the
illumination of a predetermined field of surveillance and for
giving an intrusion signal,
a B-series of similar sensor means having a significantly smaller
field of surveillance entirely within that of the sensor means of
said A-series and for giving an intrusion signal,
a sequence unit connected to said A-series and having first and
second circuits, each including a relay with latching means and
relay-operated switches and timing means for retaining the latching
of said relay for a predetermined time interval, the time interval
for said first circuit being for a relatively brief time and that
for said second circuit being for a longer time, an intrusion
signal from said A-series activating both said first and second
circuits, and
an alarm output terminal connected by said sequence unit to said
B-series through said relay switches when and only when said first
circuit has been "on" and its time interval has expired and said
second circuit is still "on" during its time interval,
whereby said alarm output terminal is energized only when an
A-series intrusion signal is followed by a B-series intrusion
signal no sooner than after the expiry of the time interval of said
first circuit but during the time interval of said second
circuit.
8. The security system of claim 7 having
a C-series of sensor means like those of said A-series but having a
field of surveillance relating to ambient light rather than a zone
to be protected from intrusion,
a lockout unit connected to said C-series and to said sequence unit
and having a third circuit like said first and second circuits and
having a time interval shorter than that of said first circuit and
means energized by a signal from said C-series for disabling a
simultaneous intrusion signal from said A-series.
9. The security system of claim 8 having a D-series of sensor means
similar to the A-series, threshold amplifier means connected to
said D-series for activation only when a predetermined threshold
illumination change has been signaled by said D-series,
alarm means activated by said threshold amplifier means for
indicating the presence of fire or explosion conditions,
a second lockout unit connected to said C-series and like the other
said lockout unit for enabling a simultaneous signal for said
D-series.
10. The security system of claim 7 having a D-series of sensor
means like those of said A-series, threshold amplifier means
connected to said D-series for activation only when a predetermined
threshold illumination change is signaled by said D-series, and
alarm means activated by said threshold amplifier means.
11. The security system of claim 10 having another sequence unit
for comparing the signals of two spaced-apart sensor means of said
D-series, and giving an "explosion" signal if the two sensor means
give simultaneous signals and a "fire" signal if the sensor means
gives its signal a few seconds later than the other said sensor
means.
12. A security system for detecting moving intruders, including in
combination
an A-series of sensor means for detecting changes in the
illumination of a predetermined field of surveillance and for
giving an intrusion signal,
a B-series of similar sensor means having a significantly smaller
field of surveillance entirely within that of the sensor means of
said A-series and for giving an intrusion signal,
a sequence unit connected to said A-series and to said B-series and
having first and second circuits, each including a relay with
latching means an relay-operated switch and timing means for
retaining the latching of said relay for a time interval, the time
interval for said first circuit being for a relatively brief time
and that for said second circuit being for a longer time, an
intrusion signal from either said A-series or said B-series
activating both said first and second circuits, and
an alarm output terminal connected by said sequence unit to said
A-series and said B-series through said relay switches when and
only when said first circuit has been "on" and its time interval
has expired and said second circuit is still "on" during its time
interval,
whereby said alarm output terminal is energized only when either an
A-series or a B-series intrusion signal is followed by another
intrusion signal from said A or B series no sooner than after the
expiry of the time interval of said first circuit but during the
time interval of said second circuit.
13. The security system of claim 12 having
a C-series of sensor means like those of said A-series but having
field of surveillance relating to ambient light rather than a zone
to be protected from intrusion,
a lockout unit connected to said C-series and to said sequence unit
and having a third circuit like said first and second circuits and
having a time interval shorter than that of said first circuit and
means energized by a signal from said C-series for disabling a
simultaneous intrusion signal from said A-series.
14. The security system of claim 13 having a D-series of sensor
means similar to the A-series, threshold amplifier means connected
to said D-series for activation only when a predetermined threshold
illumination change has been signaled by said D-series,
alarm means activated by said threshold amplifier means for
indicating the presence of fire or explosion conditions,
a second lockout unit connected to said C-series and like the other
said lockout unit for enabling a simultaneous signal for said
D-series.
15. The security system of claim 12 having a D-series of sensor
means like those of said A-series, threshold amplifier means
connected to said D-series for activation only when a predetermined
threshold illumination change is signaled by said D-series, and
alarm means activated by said threshold amplifier means.
16. The security system of claim 15 having another sequence unit
for comparing the signals of two spaced-apart sensor means of said
D-series, and giving an "explosion" signal if the two sensor means
give simultaneous signals and a "fire" signal if the sensor means
gives its signal a few seconds later than the other said sensor
means.
17. A security system for detecting moving intruders, including in
combination
an A-series of photoconductive sensor means for detecting changes
in the illumination of a predetermined field of surveillance and
for giving an electrical intrusion signal,
first mode selector means connected to said A-series for
determining whether said intrusion signal is to give positive or
negative polarity for a light increase,
first signal amplifying means connected to from said first mode
selector means,
a B-series of photoconductive sensor means having a significantly
smaller field of surveillance entirely within that of the sensor
means of said A-series and for giving an intrusion signal,
second mode selector means, like said first mode selector means,
connected to said B-series,
second signal amplifying means connected to said second mode
selector means,
a sequence unit connected to said first and second amplifier means
and having first and second circuits, each including a latching
relay with switches and timing means for retaining the latching of
said relay for a predetermined time interval, the time interval for
said first circuit being for a relatively brief time and that for
said second circuit being for a longer time, an intrusion signal
from said amplifying means activating both said first and second
circuits, and
an alarm output terminal connected by said sequence unit to at
least one said amplifying means through said relay switches when
and only when said first circuit has been "on" and its time
interval has expired and said second circuit is still "on" during
its time interval.
18. The security system of claim 17 having
a C-series of sensor means like those of said A-series but having
field surveillance relating to ambient light rather than a zone to
be protected from intrusion,
a lockout unit connected to said C-series and to said sequence unit
and having a third circuit like said first and second circuits and
having a time interval shorter than that of said first circuit and
means energized by a signal from said C-series for disabling a
simultaneous intrusion signal from said A-series.
19. The security system of claim 17 wherein said amplifying means
is in series with a gain resistor and is in parallel with a fixed
resistor and a photoconductive sensor surveying ambient light and
thereby decreasing its resistance and lowering gain of the
amplifying means as ambient light increases and increasing the gain
of said amplifying means as the ambient light gets darker.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a security system and more
particularly to a security system having transient and ambient
change lockout provisions.
Heretofore, intrusion detection systems using the ambient light
method of detection were extremely likely to give false alarms,
because the light sensors are so sensitive that they see shades of
grey which the human eye cannot see. Thus, such systems were too
discriminating, signaling intrusions when in fact there were no
intrusions. For example, alarms were given when a bird passed
through the guarded zone; even a cloud passing over the sun in the
daytime would cause enough change in the ambient light to trigger
the system. So would a car driving by at night with car lights, or
an airplane flying overhead at nighttime.
Another difficulty with prior-art, light-sensitive security systems
was that a fire on the premises would activate the lockout
circuits. A big flash from a bomb would cause the whole area to
light up and would activate all systems, but since it would
activate the lockout systems, no alarm would be given. It is
important to determine whether there is a bomb, a fire, an
intrusion, or just passing light--and to discriminate between these
different conditions.
Another problem was to provide a long-range security system.
Existing security systems are very, very short range. Hypersonic,
supersonic, and ultrasonic systems are good for only about 15 feet
at the maximum. Radio frequencies are good for only about 30 feet
at the most, and beyond these maxima is the range where they give
false alarms very readily. An object of the present invention is to
extend this range to about 100 to 200 feet, and another object is
to make it possible to have systems that look in all directions
from one point.
Other security systems have introduced wiring problems, with great
lengths of wire being required, and cost problems, due to the
expense of installation and the manpower this requires.
Another problem with prior-art security systems has been the cost
of providing standby power for the security system. Systems
heretofore in use have required relatively large amounts of power,
requiring several batteries that cost 60 to 70 dollars each.
There has also been a problem relating to the effect upon the
security system by powerlines and the like under certain
conditions. Sixty-cycle current and high-frequency current have
often in the past actually triggered an alarm system under certain
conditions. For example, when somebody put a heavy load on the main
powerline and the current dropped, for example, the power and light
companies frequently change generators at 2:00 a.m., and this gives
a sudden pulse that has given a false alarm on a nearby security
system.
Ease of installation, low power requirements, inexpensive standby
systems, systems that will operate under any conditions other than
total darkness, and systems free from false alarms are provided by
the present invention.
SUMMARY OF THE INVENTION
The security system of this invention has a plurality of sensors
such as photocells or infrared detectors grouped in clusters with
pairs of sensors placed through directing apertures for creating
inner and outer zone areas of protection, such as nearly coaxial
cones of different slope, for example. The outputs from the sensor
clusters are passed through sequencing units, which may be
programmed, for example, to yield an output only when an intruder
passes into the inner zone after passing through the outer zone and
after at least a predetermined time delay, thereby preventing the
setting off of false alarms by transient changes within the zones
that might be caused by vehicles, birds, etc.
Some sensors may be filtered, and a series of filters may be used
varying from heavy filtering to light light or no filtering, for
rendering the individual sensors sensitive to change under varying
ambient conditions. The sensors receiving minimum filtering may be
used for night operation, while the sensors receiving maximum
filtering may be used for bright daytime operation.
Alternatively, filters may be replaced with a system providing an
automatic gain for compensating for different types of light.
A series of lockout sensors are provided for sensing surrounding
ambient light conditions, their outputs being coupled to the
sequencing unit for disabling the sequencing unit during rapid
ambient changes such as lightning. These sensors may be
omni-directional or directed to the sky, for example.
Another sensor channel can be provided, if desired, for sensing a
fire, the only variation being the time delay in the sequencing
unit which, because of the nature of the phenomenon, would be
longer between the outer and inner zones of interest of protection.
A rise-time detector may also be provided for eliminating unwanted
signals.
An object of the present invention is the provision of an improved
security system.
Another object of the invention is the provision of the security
system for sensing intruders.
Another object of the invention is the provision of a security
system for sensing fires.
Yet another object of the invention is the provision of a security
system for sensing both intruders and fires.
A still further object of the invention is the provision of a
security system which is not affected by short transient
changes.
A still further object of the invention is the provision of a
security system which is not affected by rapid ambient
variations.
The system of inner and outer cones of surveillance in combination
with a sequence operation in which an initial intrusion has to be
followed by another intrusion signal, usually from the other cone,
before an alarm signal is given, makes sure that if there is an
intrusion passing from the outer cone through the inner cone and
back out through the outer cone again, an alarm will be sent to the
proper authorities. At the same time the system eliminates what is
known as "glitches", a single pulse coming from any sensor, any
amplifier. Signals from birds in flight, clouds over the sun, and
so on are eliminated.
The invention, using ambient light, provides an extended range of
surveillance--such as 100 to 200 feet from each sensor cluster.
This system also is inexpensive to install. For example, one cable
from a master unit could be run to, say, the third floor above,
where a terminal strip or distribution center is located, and then
all the sensors could be near there. This eliminates the necessity
of running individual wires to each sensor, because all the sensors
could be put in one room or close together in series or parallel,
with only one signal coming back down to say that there is an
intrusion at the surveyed area, e.g., the third floor.
As another example, for a 10 .times. 100 feet warehouse with no
partitions or a 100 .times. 100 feet open room, the control unit
could be installed in one corner, with the sensors mounted on top
of the control unit. This would see throughout the whole warehouse
or room. Such a system could be prewired, and installation would
then be nothing more than putting the sensors in place and plugging
the system into live current.
For standby power, the invention can utilize inexpensive batteries
costing only about one-half or one-third of what the batteries for
other systems cost.
Other objects and many of the attendant advantages of this
invention will become apparent with reference to the following
detailed description taken into conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a system block diagram of a security system embodying the
principles of the present invention.
FIG. 2 is a schematic diagram of one sensor of the embodiment of
FIG. 1.
FIG. 3 is a schematic representation of another sensor of the
embodiment of FIG. 1.
FIG. 4 is a schematic representation illustrating zone coverage by
a plurality of the sensors of the embodiment of FIG. 1.
FIG. 5 illustrates schematically two clusters of sensors of the
embodiment of FIG. 1.
FIG. 6 is a schematic representation of a sequence unit and lockout
circuits for the device of FIG. 1.
FIG. 7 is a schematic representation of a modified sequencing and
lockout circuit for the system of FIG. 1.
FIG. 8 is a block diagram of another security system embodying the
principles of the invention.
FIG. 9 is a diagram of an area having portions surveyed by fire
detecting sensors and portions surveyed by intrusion detectors.
FIG. 10 is a circuit diagram of a threshold amplifier for the fire
and bomb detecting and discriminating system.
FIG. 11 is a block diagram explaining the logic unit for the fire
and bomb detecting and discriminating system.
DESCRIPTION OF SOME PREFERRED EMBODIMENTS
The block diagram of FIG. 1 shows, as an example only, a security
embodying the principles of this invention, for detecting
intrusions and fires while avoiding false alarms. It has a
plurality of sensor clusters 11, 12, 13, 14, 15, 16, 17 and 18. The
sensor clusters 11 and 12 are part of a "large cone" detector
system, explained below with reference to FIGS. 3 and 4. The sensor
cluster 11 is coupled through a mode selector 19 and an amplifier
20 to one input of an inverter switch 21. The sensor cluster 12 is
coupled through a mode selector 22 and an amplifier 23 to another
input of the inverter switch 21. FIG. 5 shows the coupling of the
sensor clusters 11 and 12 to the mode selectors 19 and 22, and this
feature will be discussed below; it relates also to the coupling of
the other sensor clusters to their mode selectors. The inverter
switch 21 has an output coupled to a sequence unit 24, which in
turn, has an output coupled to an output terminal 25. The sequence
units 24 will be explained later in connection with FIG. 6.
The sensor clusters 13 and 14 are part of a "small cone" detector
system explained below with reference to FIGS. 2 and 4. The sensor
cluster 13 is coupled through a mode selector 26 and an amplifier
27 to one input of an inverter switch 28. The sensor cluster 14 is
coupled through a mode selector 29 and an amplifier 30 to another
input of the inverter switch 28. The inverter switch 28 has an
output coupled to the sequence unit 24.
The sensor clusters 15 and 16 are part of the lockout system for
the device and will be explained below in connection with FIG. 6.
The sensor cluster 15 is coupled through a mode selector 31 and an
amplifier 32 to one input of an inverter switch 33. The sensor
cluster 16 is coupled through a mode selector 34 and an amplifier
35 to another input of the inverter switch 33. The inverter switch
33 has one output coupled to a lockout unit 36 and another output
coupled to a lockout unit 37. The lockout unit 36 has an output
coupled to the sequence unit 24 and the lockout unit 37 has an
output coupled to a logic unit 38.
The sensor clusters 17 and 18 relate to the fire and bomb detection
portion of the circuit and will be explained below in connection
with FIGS. 9 and 10. No mode selector switch is required. One
particular mode is always used. The sensor cluster 17 is coupled
through a threshold amplifier 39 and an amplifier 40 to one input
of an inverter switch 41. The sensor cluster 18 is coupled through
a threshold amplifier 42 and an amplifier 43 to another input of
the inverter switch 41. The inverter switch 41 has an output
coupled to the logic unit 38, explained further in FIG. 11. The
logic unit 38 has an output coupled to an output terminal 44.
A "SMALL-CONE" SENSOR (FIG. 2)
FIG. 2 shows a sensor 45, which is one of the sensors of the
clusters 13 and 14. The sensor 45 has a light sensing element 46
with output terminals 47 and 48 located within a housing 49. The
housing 49 has an aperture 50 at one end thereof. Diverging lines
51 and 52 indicate the cone of surveillance provided by the
combination of the sensing element 46, the housing 49, and the
aperture 50. They indicate the volume of a zone from which ambient
light can pass via the aperture 50 to the sensing element 46.
Ambient light from outside the volume defined by the lines 51 and
52 cannot affect the sensing element 46. Since the cone 51,52 is
relatively small in angle, it is called a "small cone," and the
sensor 45 is called a "small cone sensor."
Different types of sensing elements 46 may be used, some being more
sensitive than others at various points in the visible spectrum.
For instance, some systems of this invention use primarily sensing
elements 46 housing maximum sensitivity at 5,500 angstroms.
However, for operation in artificial light, the system may better
use sensing elements 46 whose maximum sensitivity lies at about
6,200 angstroms. Cadmium sulfide and cadmium selenide sensing
elements 46 are often preferred, as photoconductive bulk effect
cells.
A "LARGE-CONE" SENSOR (FIG. 3)
FIG. 3 shows a light sensor 53 including another sensing element 46
with output leads 47 and 48 within a housing 54 having an aperture
55 at one end thereof. Diverging lines 56 and 57 define a wider
angle than do the lines 51 and 52; so they define a "large cone,"
and the sensor 53 is a "large cone sensor." The sensor 53 is one of
several sensors used in each cluster 11 and 12. Ambient light from
within the cone can affect the sensor 53, and ambient light outside
the cone cannot affect it.
A filter 58 is shown here, filtering ambient light. Such a filter
may or may not be present in either the sensor 45 (or any other
inner-cone filter) or in the sensor 53 (or any other outer-cone
filter). The purpose of such a filter, if employed, is to reduce
the quantity of light sent to the sensing element 46 and thereby to
increase the ability of the sensing element 46 to see light changes
in bright light. By having some sensors of a cluster filtered and
other unfiltered, the sensitivity range of the cluster can be
increased.
LARGE CONE-SMALL CONE COMBINATION (FIG. 4)
FIG. 4 schematically shows a sensor arrangement 60 in which a
sensor 45 and a sensor 53 are located closely adjacent to each
other and are spacially displaced from another schematically shown
sensor 45' and sensor 53'. The sensor 53 has an outer zone of
surveillance shown schematically by a cone 61 and the sensor 45 has
an inner zone of surveillance shown schematically by a cone 62. The
sensor 53' has an outer zone of surveillance shown schematically by
a cone 63, and the sensor 45' has an inner zone of surveillance
shown schematically by a cone 64. The significance of the
combination of outer and inner zones has already been alluded to
and will be explained later in more detail. The reason for the
facing sensor group 45,53 and 45',53' is so that one group can
protect another from tampering by someone coming up behind one
group.
SENSOR CLUSTERS AND MODE SELECTORS (FIG. 5)
In FIG. 5, a supply voltage is applied at an input terminal 65,
there being a ground 66. The input voltage from the terminal 65
passes through a resistance 67 to sensing elements 53,53a and 53b
and thence via a resistance 68 to the ground 66. Another path from
the input terminal 65 to the ground 66 goes via a resistor 69,
sensors 53p, 53q and 53r and a resistor 70.
The sensors 53, 53a and 53b represent the sensor cluster 11. Of
course, there may be more or fewer sensors in the cluster 11, but
these three give the general idea of clustering sensors. Each
sensor can be considered as being substantially identical to the
sensor 53 as shown in FIG. 3, either with or without the filter
shown there. Similarly, the sensors 53p, 53q and 53r can represent
the sensor cluster 12; although again there may be more or fewer
sensors. In each instance, the sensor may be like the sensor 53
shown in FIG. 3, with or without the filter.
The mode selector 19 comprises a switch arm 71 and two terminals 72
and 73. The switch arm 71 rests against one of the two terminals 72
and 73 at any one time but not against both, and a lead 74 from the
switch 71 goes to the amplifier 20 (see FIG. 1). The effect is to
choose either a positive-going signal or a negative-going signal
according to the needs of the system which follows the mode
selector. Thus, the terminal 72 is connected in between the
resistor 67 and the sensor 53, while the terminal 73 is connected
in between the sensor 53b and the resistor 68. Thus, a
positive-going signal will be produced by an increase in ambient
light if the mode selector switch 71 rests against the terminal 73,
while the same increase in light would produce a negative-going
signal at the terminal 72. Depending on the situation involved, the
user may wish to use either one of these two terminals 72 and 73 to
place the system in a desired mode.
The mode selector 22 is substantially identical to the mode
selector 19 in structure and is exactly analogous in connection.
Thus, there is a switch 75 between two terminals 76 and 77. The
terminal 76 is connected between the resistor 69 and the sensor
53p. The second terminal 77 is connected between the sensor 53r and
the resistor 70. The switch arm 75 acts to select either a signal
which goes positive with an increase in light to the sensors or one
which goes negative with the same increase, and a lead 78 connects
the switch arm 75 to the amplifier 23.
Each mode selector 19, 22, 26, 29, 31 and 34 thus enables the
selection between two signals, one of which is positively actuated
by an increase in light and the other of which is positively
actuated by a decrease in light. For example, an intruder wearing a
dark suit would certainly cause a decrease in the ambient light in
the zone, whereas an intruder carrying a flashlight at night would
certainly cause an increase. Thus, any mode selector may be changed
between night and day, if that is desired.
The connection of each of the mode selectors to its sensor cluster
is the same.
SEQUENCING AND LOCKOUT (FIG. 6)
Referring for the moment to FIG. 1, the connections of all the
sensor clusters to their respective mode selectors has been
explained, and the connection of each mode selector through an
amplifier to an inverter switch is apparent. Each of the inverter
switches 21, 28, 33 and 41 changes a negative signal to a positive
one and passes positive signals.
The present section explains the action of the sequence unit 24 and
the lockout unit 31.
A lead 80 (see FIGS. 1 and 6) connects the inverter switch 21 for
the A-series system to the sequence unit 24, while a lead 81
connects the inverter switch 28 for the B-series system to the
sequence unit 24. The basic idea here is to prevent either the
A-series system or the B-series system alone from actuating an
alarm. In order for there to be an alarm in the system of FIG. 6,
the A system sensors 53, etc., must first indicate an intrusion
into one of the large cones 61 (or 63) and then the B system
sensors 45, etc., must indicate an intrusion into one of the small
cones 62 (or 64). Furthermore, the B intrusion signal must follow
the A intrusion by at least a predetermned time interval--for
example, no sooner than 4 seconds apart. Still further, the B
intrusion signal must follow the A signal within a longer
predetermined time interval--for example, before the lapse of 24
seconds. The idea is to prevent false alarms by bodies which move
more swiftly than men and by two sporadic bodies. Finally, a
lockout unit 41 is connected to the Series C sensor prevents
actuation simply by a sudden or gradual change in general ambient
light level. (It should be remembered that the Series D sensors are
used for fire and explosion detection, and they are treated below
in connection with FIG. 9.)
The lead 80 goes to a bus line 82, and when the sensor clusters 11
and 12 give an intrusion signal, there is a momentary flow of
current through a relay coil 83 and through a transistor 84, which
is also connected to a common bus line 85 that is normally
grounded, as will be explained later. In parallel with the relay
coil 83 is a diode rectifier 86 which shunts out reverse-flow
current through the relay coil 83.
The relay coil 83, when energized throws two switches 83a and 83b.
These switches 83a and 83b normally rest against respective
terminals 83c and 83d, the terminal 83c being an open circuit. When
the relay coil 83 is energized, the switches 83a and 83b rest
against the terminals 83e and 83f, respectively, the terminal 83f
being an open circuit. The terminal 83d is connected by a lead 87
to the output terminal 25, to give the intrusion alarm. The
terminal 83e is connected in between two diodes 88 and 89.
A B+ voltage input 90 is connected by a lead 91 to the switch 83a;
hence when an A-series intrusion signal even momentarily energizes
the relay coil 83, the B+ voltage from the input 90 is connected by
the switch 83a, terminal 83e, the diode 88, and the bus line 82 to
the coil 83, latching the coil 83 on, even though the initial
actuating signal--the sensed Series A intrusion signal--is very
brief. Moreover, a resistor 92 connects the bus line 82 to the base
of the transistor 84 and keeps it in conductive mode as long as the
bus line 82 is supplied by B voltage of the proper polarity,
supplying the needed base current. A capacitor 93 shunts any A-C
components to the ground bus line 85. Thus, when there is an
intrusion signal by the A-series of sensor clusters 11 and 12,
passing through the mode selectors 19 and 22 and the amplifiers 20
and 23 to the inverter switch 21, a signal is transmitted via the
lead 80 from the inverter switch 21 to the sequence unit 24 which
causes the transistor 84 to conduct and to keep conducting. At
first, a small base current flows, and then that is multiplied by
the transistor's gain which may be many times the amount, for
example, the gain may be 40.
The instant the transistor 84 starts to conduct, a timing capacitor
94 starts to be charged through a fixed timing resistor 95 and a
variable timing resistor 96. The variable resistor 96 makes it
possible to change the R-C time constant provided by the
combination of the resistors 95 and 96 with the capacitor 94. For
this particular portion of the sequence unit 24 the time constant
may be about four seconds, which means that the relay 83 will
remain energized for four seconds.
Connected to the capacitor 94 and the resistor 96 is the base of
unijunction transistor 97 having one anode connected through a
resistor 98 to the bus line 82 and another anode connected to the
common bus line 85, which is grounded except where the lockout unit
36 is energized. When the capacitor 94 charges up to where the
junction of the resistor 96 and the capacitor 94 has reached the
predetermined point set by the characteristics of the particular
unijunction transistor 97 that has been picked, then the
unijunction transistor 97 fires and discharges its capacity through
to ground. The big negative pulse that then results at the junction
of the capacitor 94 and the resistor 96 and the base of the
transistor 84, then cuts off the transistor 84, deenergizing the
relay coil 83 and the switches 83a and 83b then return to the
positions shown in FIG. 6.
The diode 89 connects the relay switch terminal 83e to a bus line
100, which is part of a circuit that, except for time constants,
substantially duplicates that of the bus line 82. Thus, there is a
relay coil 101 in parallel with a diode 102, connecting the bus
line 100 to a transistor 103. The relay coil 101 controls switches
101a and 101b, with terminals 101c, 101d, 101e and 101f, the
terminals 101c and 101d being open circuits. The terminal 101e
latches the relay 101 energized immediately after the relay 83
closes the switch 83a against the terminal 83e and holds the relay
energized after the switch 83a moves away from the terminal 83e,
e.g., after the 4-second delay interval determined by the R-C
circuit 94, 95 and 96.
A resistor 104 and condenser 105 correspond to the resistor 92 and
condenser 93. A timing capacitor 106, a fixed resistor 107 and a
variable resistor 108 provide an R-C constant that gives a longer
time than do the elements 94, 95 and 96--for example, 24 seconds
instead of four seconds. A resistor 109 and a unijunction
transistor 110 complete this circuit and perform functions like
those of their corresponding elements in the other timing
circuit.
The purpose is this: to prevent any reaction or any alarm being
given even if the A-series sensor clusters 11 and 12 indicate an
intrusion unless at least 4 seconds later the B-series of sensor
clusters 13 and 14 indicates an intrusion, and to cut the whole
thing off if there is no signal from the B-series sensors for a 24
second period. Thus, the relay coil 83 may stay energized for about
4 seconds and the relay coil 101 may stay energized for about 24
seconds. These figures are, of course, examples but they have
actually been found to be good times to use in actual
circuitry.
The lead 81 is connected to the switch 101b, which normally nests
against the terminal 101d, an open circuit. However, when the
switch 101b is urged by the energized relay coil 101 against the
terminal 101f, the lead 81 is connected by a lead 111 to the switch
83b. Thus, during the (for example) 24-second period of
energization of the coil 101, the lead 81 is connected to the lead
111. However, during the (for example) 4-second period of
energization of the coil 83, the lead 111 goes via the switch 83b
to the open-circuit terminal 83f. So, a signal from the B-series
sensor clusters 13 and 14 during the four-second period following a
signal from the A-series sensor clusters 11 and 12 will not
initiate a signal. But after the 4-second period, the coil 83 is
de-energized, and then the switch moves back to rest against the
terminal 83d, connecting the lead 111 to the lead 87 and therefore
to the output terminal 25. Hence, an intrusion signal from the
B-series sensor clusters 13 and 14 which follows more than four
seconds after an A-series intrusion signal and within 24 seconds
after that signal will sound an intrusion alarm--unless the lockout
unit 36 was activated when the A-series signal was given.
The lockout unit 36 is also shown in FIG. 6. The Series D or
lockout sensor clusters 15 and 16 may be substantially the same as
those of the Series A and B clusters, but are pointed toward a
different area. The Series C sensor clusters 15 and 16 are
typically pointed to the sky or to some area which gives a general
ambient lighting but which does not respond to the area over which
the security is being desired; if the signal is the same for the
sensors 11, 12, 13, 14, 15 and 16, the lockout unit 36 will be
energized and as will be shown, this will prevent the sequence unit
24 from delivering the signal which would otherwise be an alarm
signal, to the output terminal 25.
The sensor clusters 15 and 16 give their signals to their
respective mode selectors 31 and 34 and to their respective
amplifiers 32 and 35 and to the inverter switch 33. The inverter
switch 33 sends its output by a line 112 to the lockout unit 36. As
shown in FIG. 6, the lockout unit 36 has exactly the same basic
structure as either of the two sequence circuits. Thus, it has a
bus line 113, a relay coil 114, a transistor 115, a diode 116, a
resistor 117, and a condenser 118 connected to a permanently
grounded bus line 119. It has a timing capacitor 120 which is
coupled to a fixed resistor 121 and a variable resistor 122 and to
a unijunction transistor 123 having one anode connected to a
resistor 124 while the other anode is connected to the ground line
119.
The relay coil 114 throws switches 114a and 114b. The switch 114a
latches the relay 114 by moving from a blank terminal 114c to a
latching terminal 114e, thereby connecting the B+ input 90 to the
relay coil 114 through the lead 91. The switch 114b accomplishes
the lockout. Normally, the switch 114b rests against the terminal
114d, and it then connects the bus line 85 of the sequence unit 24
to ground, through the bus line 119, where the relay coil 114 is
energized, the switch 114b opens this circuit and rests against an
open-circuit terminal 114f, thereby destroying the connection to
ground of the bus line 85, so that the relay 83 cannot be
activated, nor can the relay 101. The latching circuit holds the
lockout relay 114 on for a desired time, which may typically be
from 2 to 4 seconds, depending on the resistance-capacitance
characteristics chosen for this particular part of the circuit.
Thus, no intrusion alarm signal can be given if the lockout unit 36
is activated, nor can an intrusion alarm be given during the
4-second (or other appropriate delay period) during which the relay
83 is energized nor can such a signal be given after the delay
period (typically 24 seconds), during which the relay 101 is
energized. An intrusion signal will sound the alarm only if the
Series A sensor clusters 11 and 12 are first energized without
energization of the Series C lockout sensor clusters 15 and 16 and
if during the time that the relay 83 is de-energized and the relay
101 is still energized there is a second intrusion signal given by
the Series B sensor clusters 13 and 14. As a result of this, many
causes of false alarms are eliminated from the system. A bird
passing through the area would energize both the signal 80 and the
signal 81 within the four-second delay period, so that no alarm
would be given. A man walking through would give a completely
different result, for he would go from the outer cone to the inner
cone in a period that would take longer than 4 seconds. It should
also be noted that anything such as lightning flash or passing
cloud which would energize both of the signals 80 and 81
simultaneously would not produce an alarm signal.
A MODIFIED FORM OF SEQUENCE CIRCUIT (FIG. 7)
The circuit of FIG. 7 is very similar to that of FIG. 6 and in most
particular is identical, so that identical numbers have been used
in most of the circuits. The difference in operation is as follows:
In the circuit of FIG. 6, the A-series or large-cone sensor
clusters 11 and 12 have to be actuated first, and no alarm is given
if they are actuated again even during the 20-second active period
following the four-second delay. In the FIG. 7 circuit either the
A-series or the B-series may be activated first, and an alarm
circuit will follow upon either one of them being actuated within
the 20-second period following the 4-second delay. (Other times may
be used, of course.)
Thus, in FIG. 7 the inputs 80 and 81 are tied together to a lead
125, which goes to the switch 101b where the relay 101 is not
energized. The switch 101b rests on the contact 101d, which is
connected to the bus line 82 by a lead 126, so that the signals
from inputs 80 and 81 will have exactly the same effect. Thus, if
there is a primary signal from either the input 80 or the input 81,
the sequence unit 24 will be activated, and nothing will happen if
there is another signal from either one of them during the delay
period while the relay 83 is energized, which means during the
first four seconds. Such a signal energizes the relay coil 101 (via
the latching circuits) and therefore moves the switch 101b away
from the terminal 101d and against the terminal 101f, whence the
lead 91 goes to the switch 83b, which is open during the 4-second
delay period. However, after that four-second delay period and
before the deactivation period of the relay 101 which may be 24
seconds, another signal from either input 80 or 81 will go via the
lead 91 and switch 83b to the lead 87 and give the alarm at the
output terminal 25. The circuits being otherwise identical, there
is no need to discuss the operation of the lockout unit 36 again,
for it is exactly the same as it was before.
A MODIFIED FORM OF DETECTION SYSTEM HAVING A DIFFERENT SENSITIVITY
DEPENDING ON THE AMOUNT OF AMBIENT LIGHT
FIG. 8 shows a circuit which is basically the same as that of FIG.
1, and the same numbers have been given to the same parts. The
differences are that in each one of the circuits one of the sensor
clusters is provided with a network that is in parallel with its
amplifier.
Thus, the sensor cluster 11 going through the mode selector 19 to
the amplifier 20 and then to the inverter switch 21 has, in
parallel with the amplifier 20, a parallel network comprising a
capacitor 130 and, in parallel with that, a resistor 131 in series
with a light sensor 132 the resistance of which drops with an
increase in light, as is the case with the sensor 53. Also in
parallel with that sensor 132 is a resistor 133. The sensor 132
looks at the same light as a sensor 53 in the sensor cluster.
The resistance of sensor 132 varies from a small amount in bright
light (e.g., 1,000 ohms) to a large amount (e.g., 700,000 ohms) in
dim light. Since the gain of the amplifier 20 is the ratio of the
parallel resistance (the resistance of the network 131, 132 and
133) to the input resistance, the gain will change greatly as the
day gets darker and approaches or reaches night. (The capacitor 130
merely routes A-C current around the amplifier 20.) Thus, if
R.sub.IN, the input resistance is 10,000 ohms, and the resistance
of the resistor 131 is 1,000,000 ohms, then in bright daylight,
when the resistance of the sensor 132 is 1,000 ohms, the gain of
the amplifier 20 will be 100.1, while in darker conditions, when
the resistance of the sensor 132 is 700,000 ohms, the gain will be
170--in both cases excluding the resistor 133. The resistor 133 is
used to prevent the development of too much gain, holding it down
to perhaps 150 at the most and gives a gain curve more nearly in a
straight-line relationship to the light.
This structure obviates the use of filters and yet gives the system
increased sensitivity in dim light and in darkness.
FIRE AND BOMB DETECTION AND DISCRIMINATION (FIGS. 9-11)
In FIG. 9, sensors a.sub.1, a.sub.2, a.sub.3, b.sub.1, b.sub.2 and
b.sub.3 are intrusion detection sensors corresponding to a sensor
cluster 11 (for a.sub.1, a.sub.2 and a.sub.3) and to a sensor
cluster 12 (for b.sub.1, b.sub.2 and b.sub.3).
Sensors c.sub.1, c.sub.2 and c.sub.3 are fire-and-bomb-detection
sensors and correspond to a sensor cluster 17. The sensors c.sub.1,
c.sub.2 and c.sub.3, while being shown as a total of three sensors,
may represent as many as 30 or 40 individual sensors, depending
upon the area and volume to be protected.
According to the manufacturer, one cell that can be used as a
sensor c.sub.1, c.sub.2 or c.sub.3 has a resistance of
approximately 15 megohms at 0.01 foot candles of illumination and a
resistance of 0.012 megohms at an illumination of 100 foot candles.
Actual laboratory measurements of such a cell showed a resistance
of 600 ohms under normal lighting (approximately 150 foot candles)
and a resistance of 0.8 megohms when all lights were
extinguished.
Fire and bomb explosion detection sensors c.sub.1, c.sub.2 and
c.sub.3 (and the sensor clusters 17 and 18) are always installed in
the mode whereby an increase in the ambient light, within the area
being guarded, produces an increase in the sensor output voltage.
This corresponds to the mode wherein the output terminals 73 or 77
are used in FIG. 5, but there is no mode selector switch.
The threshold amplifiers 39 and 42 are always biased such that it
requires a signal lighter than the ambient lights to create an
output signal. For example, in one system of this invention, the
threshold amplifier 39 is always biased 1.1 times maximum ambient
while threshold amplifier 42 is always biased 1.3 times maximum
ambient.
Suppose that measurements showed that the maximum lighting of a
particular area was 110 foot candles. Then the minimum resistance
attained under ambient conditions by a sensor cell c.sub.1, c.sub.2
or c.sub.3 would be in the order of 1,000 ohms.
In FIG. 10, the sensor c.sub.1 is in a circuit having a B+ input
140, a resistor R.sub.1 between the input 140 and the sensor
c.sub.1 and a resistor R.sub.2 between the sensor c.sub.1 and
ground. If the B+ input is 12 volts and if R.sub.1 = R.sub.2 =
1,000 ohms, then that sensor circuit would produce an output signal
of four volts when the area was under maximum lighting conditions.
The threshold amplifier 39 is set, under these conditions, to
require (1.1 .times. 4) = 4.4 volts for activation, and it will
never produce output signals so long as the fluctuations of the
ambient lighting remains below the normal maximum, e.g., 110 foot
candles.
In the event there is a fire, however, the ambient lighting may
increase to 150 foot candles or greater, and the resistance of the
sensor c.sub.1 would then decrease below 1,000 ohms to, say, about
300 ohms, and the output signal would then be 5.2 volts. Since this
signal is greater than the 4.4 volts that bias the threshold
amplifier 39, the signal is passed on to the amplifier 40 (FIG. 1),
which amplifies that signal and passes it to the electronic switch
41 where it goes on to the logic unit 38 as a "fire" signal, and an
appropriate alarm signal is emitted.
As the fire increases in intensity it may or it may not produce
enough illumination to generate a large enough output voltage to
overcome the threshold voltage of a second threshold amplifier 42.
Should this occur, the time difference between activation of the
threshold amplifiers 39 and 42 enables the logic circuits to
determine that it is a fire, not an explosion, and that it is
growing in intensity.
Should there be a bomb explosion there will be a tremendous
increase in illumination for a very short period (in the order of
15 to 20 milliseconds), and the resistance of sensor clusters 17
and 18 will decrease to values below 100 ohms. Therefore, output
voltages will approach 6V, thereby activating both threshold
amplifiers 39 and 42 simultaneously. These two signals, arriving at
the logic unit 38 at the same time are passed through an AND gate
which produces a positive output indicating that a bomb has
exploded.
It is to be understood that the sensors may be connected in
parallel as well as in series and, in some instances, it is
preferable to use a series-parallel combination.
FIG. 10 is a more detailed interpretation of the
fire-and-bomb-detection circuitry indicating the threshold
amplifier 39, which is just like the threshold amplifier 42 in
circuitry. This view illustrates, among other points, why signals
of a value less than the signals produced by the sensors at maximum
ambient lighting cannot activate the threshold amplifiers 39 and
42, and so are never seen at the input of amplifiers 40 and 43.
In FIG. 10, the sensor cluster 17 is represented by the sensor
c.sub.1. The sensor c.sub.2 is a reference sensor. Between the B+
terminal 140 and ground the two sensors c.sub.1 and c.sub.2 are in
parallel, with the sensor c.sub.2 having a variable resistor
R.sub.3 between it and the terminal 140, and a fixed resistor
R.sub.4 between it and ground. The resistor R.sub.3 may be adjusted
until the voltage output of the sensor c.sub.2 is identical to that
of the sensor c.sub.1 when they are looking at the same light. The
voltage from the sensor c.sub.1 is applied through a lead 141 to
the plus (+) input of a first amplifier A.sub.1, and the voltage
output of the sensor c.sub.2 is applied through a lead 142 to the
negative (-) input of the amplifier A.sub.1. The amplifier A.sub.1
is so structured that a signal applied to its upper negative (-)
terminal, as is the case with the lead 142, is inverted in
polarity, while the signal applied to its plus (+) terminal, as in
the case of the lead 141, produces an output of the same polarity.
That is what the minus and plus symbols mean. Thus, if the two
signals 141 and 142 are exactly equal, the voltage output from the
amplifier A.sub.1 to the lead 143 will be zero. So long as this
adjustment is maintained and so long as the sensors c.sub.1 and
c.sub.2 are looking at the same intensity of light there will be no
signal output from the amplifier A.sub.1.
The amplifier A.sub.1 has in parallel therewith a capacitor
C.sub.1, which is a frequency-determining device for amplification,
and a gain resistor R.sub.5. It also has B+ and B- terminals as
shown.
The amplifier A.sub.1 feeds its output via lead 143 to a diode
network consisting of diodes D.sub.1 and D.sub.2 facing in opposite
directions. This network gives the system a little leeway, to avoid
making the device too responsive, with too great a sensitivity.
Because of the diodes D.sub.1 and D.sub.2 there has to be an output
fluctuation of greater than at least 0.6 volts in order to break
down the voltages on the two diodes D.sub.1 and D.sub.2 and enable
conducting to the second amplifier A.sub.2. The purpose is again to
help prevent a false alarm from such things as mice running across
the floor.
Resistors R.sub.6 and R.sub.7 are load resistors for the amplifier
A.sub.2, which again has an upper inverting negative (-) terminal
and a lower non-inverting plus (+) terminal and again has a
frequency-determining capacitor C.sub.2 and a gain resistor
R.sub.8.
The output from the amplifier A.sub.2 is fed to a logic circuit of
the kind called a CMOS circuit. The idea is that one obtains a high
voltage output from a low voltage input and vice versa. This logic
circuit includes two oppositely facing diodes D.sub.3 and D.sub.4,
the diode D.sub.3 leading directly to a logic unit B.sub.1. The
diode D.sub.4, which faces in the opposite direction, is in series
with a resistor R.sub.9 and a transistor Q.sub.1. The transistor
Q.sub.1 is provided with a resistor R.sub.10, a resistor R.sub.11
and a biasing resistor R.sub.12 that goes from the base of the
transistor Q.sub.1 to ground. A B+ voltage is applied through the
R.sub.10 and R.sub.11 resistances respectively to the base and to
the collector of the transistor Q.sub.1 and the emitter is sent to
ground. The output signal goes to the logic unit B.sub.1 via a lead
146. Under normal circumstances with no signals from the amplifier
A.sub.2, the transistor Q.sub.1 conducts very heavily and gives
zero volts through the logic unit. A large negative signal from the
lead 145 will cause current to flow down through the diode D.sub.4
through the resistor R.sub.9 and through the resistor R.sub.12 to
ground, causing a high negative voltage at the top of the resistor
R.sub.12 which completely cuts off the transistor Q.sub.1. When the
transistor Q.sub.1 is cut off, no more current flows up to the
resistor R.sub.11 to the B+terminal; therefore the junction of the
resistor R.sub.11 and the collector of Q.sub.1 goes immediately to
the value of the power supply voltage, which in this case may be
around ten volts. This puts a high signal on a pin 151 of the logic
unit B.sub.1.
The logic unit B.sub.1 has input pins 150 and 151 and an output pin
152, and the logic unit B.sub.2 has input pins 153 and 154 and an
output pin 155. These units B.sub.1 and B.sub.2 are CMOS flip-flop
generators with low power, CMOS meaning copper-metal-oxide-selenium
conductors. The high signal on the pin 151 causes the pin 152 to go
to a low voltage, according to the CMOS logic, and that in turn
causes the pins 153 and 154 of the logic unit B.sub.2 to go low,
and therefore the pin 155 immediately goes to a high output
voltage, which is a high signal capable of operating a relay at the
output signal 44. The high signal generated at the pin 155 of the
unit B.sub.2 is the result of a high negative-going signal out of
the amplifier A.sub.2, thus giving one condition.
A positive signal from the amplifier A.sub.2 is passed directly
through the diode D.sub.3 to the pin 150 of the unit B.sub.1
causing that point to go high, and when that point goes high the
pin 152 goes low again as a result of the positive signal. Since
the pin 152 is tied directly to the pins 153 and 154 of the unit
B.sub.2, they both go low, and the voltage at the pin 155 goes high
again. So, regardless of what kind of voltage comes out of the
amplifier A.sub.2 --so long as there is an output--there will be a
high signal out of the pin 155 of the unit B.sub.2.
Turning now to FIG. 11, when a fire begins and the local lighting
increases above ambient to a value greater than 1.1 times ambient,
the threshold amplifier 39 conducts and causes a signal to appear
at the input of amplifier 40. This signal is amplified and a
positive signal, greater than 5 volts, is applied to the input of
an OR gate 160. The OR gate 160 causes a positive pulse to appear
at the output 161 of the OR gate 160. This signal now becomes a
pulse to pull in a relay, drop out a relay, or to use in any way to
indicate a fire, and it goes to the output terminal 44. The signal
at 161 is also used to start a timer 162 approximately 0.1 second
after the pulse at 161 is generated. This timer 162 generates a
negative pulse which is applied to one input of an AND gate 167 and
held for 5 minutes, thus inhibiting any signals coming from the
bomb detection sensors 18 and the threshold amplifier 42. If the
fire increases in intensity, whereby the threshold amplifier 42 is
activated within five minutes of detection, the signals from the
bomb explosion detection circuits will not pass the AND gate 163,
due to the inhibiting signal generated by the timer 162.
Should there be a bomb explosion at the beginning, then both
threshold amplifiers 32 and 42 will be activated simultaneously,
and positive signals will appear at all inputs of the gate 160 and
an OR gate 164, causing positive outputs at 165 and 161. Since
timer 162 does not start until the pulse from the output 161 has
been present for 0.1 second, there will be a positive signal
present at both inputs of the AND gate 163 and a positive signal
will appear at an output terminal 166 from the AND gate 163. This
will be a positive pulse and can be used as desired to indicate a
bomb explosion.
To those skilled in the art to which this invention relates, many
changes in construction and widely differing embodiments and
applications of the invention will suggest themselves without
departing from the spirit and scope of the invention. The
disclosures and the description herein are purely illustrative and
are not intended to be in any sense limiting.
* * * * *