Interactive surveillance device

An automated interactive surveillance device provides passive infrared surveillance of a predetermined area to determine if an intruder enters the area. When the passive infrared detectors detect such an intruder, the device acts to aim a camera and ultrasonic rangefinder in the appropriate direction. The rangefinder determines the precise distance from the device to the intruder, whereupon the camera is accurately focused, the focal length adjusted for a relatively narrow field of view providing good resolution at the selected distance, and the angular elevation of the camera is adjusted appropriately. The passive infrared detectors may cooperate with a program to determine an approximate size for the detected intruder, based upon the amount of heat detected and the range determined by the ultrasonic rangefinder, to thus determine whether or not a human threat exists. The device may be elevated, with programming considering camera height, range to the intruder, and amount of heat detected to determine the approximate height of the intruder and aim the camera accordingly for a high resolution facial shot. One or more devices as needed may be connected to a remote monitoring site.

FIELD OF THE INVENTION 
The present invention relates generally to automated electronic security 
devices, and more specifically to an automated surveillance device using a 
plurality of passive infrared sensing devices to determine azimuth and an 
ultrasonic transceiver to determine range and resulting elevation for an 
elevated camera. 
BACKGROUND OF THE INVENTION 
The monitoring of areas for various purposes, such as traffic control, 
animal or human intrusion deterrence, and/or surveillance for security or 
other purposes, has become increasingly important with population 
increases and the pressures of a more complex society. Such concerns are 
often apparent to the observer, who may readily note remote camera 
installations and security guards and personnel in banks, shopping malls 
and other areas, as well as pneumatic or other traffic monitoring devices 
on the road. Such devices and services can be relatively costly, 
particularly in the case of monitoring or security personnel. However, in 
some situations there have been no suitable alternatives to such personnel 
due to the relatively high power demands of many security systems, such as 
floodlighting for camera surveillance, etc., as well as the need for human 
observation. 
The need arises for a surveillance system which is capable of operating 
upon demand, i.e., when an intruder or intruders approach the area covered 
by the system. The system should require relatively low power in normal 
use, as the additional power required for lights, audio devices, cameras, 
etc. need only be supplied when required by the primary sensing means. The 
primary sensing means should be of a passive nature, which renders such 
sensing means more difficult to detect, as well as further reducing power 
demands and costs. The system should respond to the needs of surveillance 
security, by providing a relatively high resolution, narrow field of view 
video of any intruder in the area, by means of a secondary range 
determination system providing input to a camera control for elevation and 
control of the focal length thereof. Moreover, the system should be 
relatively inexpensive to manufacture and operate in comparison to other 
systems developed. 
DESCRIPTION OF THE PRIOR ART 
U.S. Pat. No. 2,700,318 issued to James Snyder on Jan. 25, 1955 discloses a 
Gun Muzzle Blast Indicator using fixed lenses and progressive density 
filters. Light from the blast will strike the filters at different points, 
depending on the direction of the blast relative to the lens orientation. 
The device determines only direction and is incapable of determining range 
or elevation, or of interacting with another device (e.g., camera or 
rangefinder). 
U.S. Pat. No. 2,961,545 issued to Robert W. Astheimer et al. on Nov. 22, 
1960 discloses a Tracker For Moving Objects directed primarily to the 
tracking of rockets and/or high speed aircraft having significant heat 
radiation. The device uses two passive infrared detectors (PIRs), each 
having a relatively wide field of view, for azimuth and elevation, and two 
additional PIRs, each having a relatively narrow field of view, for "fine 
tuning" of the azimuth and elevation of the target. The device is 
completely passive, and thus is incapable of providing range information. 
U.S. Pat. No. 3,703,718 issued to Herbert L. Berman on Nov. 21, 1972 
discloses an Infrared Intrusion Detector System using a single PIR 
detector and a series of mirrors or lenses to broaden the field of 
coverage of the detector. While the system may be activated by the passage 
of a heat source across the mirror or lens array, no means is provided to 
pinpoint either the direction or the distance of the heat source nor to 
activate any camera or recording means, as a camera could not be aimed by 
the device with sufficient precision to be useful. 
U.S. Pat. No. 3,760,399 issued to Frank Schwarz on Sep. 18, 1973 discloses 
an Intrusion Detector having a thermopile sensor comprising a plurality of 
thermocouples. The device depends upon movement of a heat source across 
the plural thermocouples to create a varying voltage to trigger an alarm. 
The device is thus incapable of pinpointing a specific direction or 
azimuth for an intruder, or of determining range, thus rendering the 
device unsuitable for use with a camera. 
U.S. Pat. No. 3,924,130 issued to Allen Cohen et al. on Dec. 2, 1975 
discloses a Body Exposure Indicator which may detect infrared radiation 
from intruders or other sources in the field covered by the device. The 
device utilizes a mapping system which stores the standard field of view 
into memory, and a comparator which triggers an alarm when the scanned 
field does not match the mapped field. Cohen et al. disclose the use of a 
camera having a relatively narrow field of view, so as to pick out 
individuals in the scanned field as does the present invention. However, 
Cohen et al. fail to disclose any means for aiming the camera precisely in 
the scanned field, nor of determining range or vertical angular elevation 
to the infrared source in the field in order to focus a camera accurately, 
as in the present invention. 
U.S. Pat. No. 4,769,545 issued to Jacob Fraden on Sep. 6, 1988 discloses a 
Motion Detector comprising a single PIR detector having a relatively wide 
angle field of view. Fraden notes that such devices react to changing 
temperatures, and thus relies upon two intertwined electrodes to detect an 
infrared source. As the source crosses the electrodes, a temperature 
difference will be detected and converted to an electrical signal. 
However, the relatively wide field of view results in essentially the same 
signal being created at any time an intruder crosses any part of the field 
of view; the device is incapable of pinpointing the specific azimuth or 
elevation of an intruder. Accordingly, no camera is provided due to the 
inability of the device to aim such a camera precisely. 
U.S. Pat. No. 4,772,875 issued to James F. Maddox et al. on Sep. 20, 1988 
discloses an Intrusion Detection System which includes a plurality of 
different types of sensors in a horizontal radial array, with additional 
sensors rotatable relative to the first sensor array. The device is a 
mobile robot and is incapable of continually scanning a given field due to 
the need to stop any motion of the robot to confirm whether changes in the 
status of the sensors are due to motion of an intruder or to motion of the 
robot. The present invention is permanently installed and affixed to a 
permanent structure, which eliminates such problems. The Maddox et al. 
device utilizes radar or "microwave sensors" for range finding to an 
intruder and a plurality of ultrasonic transducers positioned around the 
body portion for maneuvering and collision avoidance, although the 
possible use of a single ultrasonic device for the determination of range 
to an intruder is also noted. As the mobile Maddox et al. robot may only 
be used on a smooth, relatively level surface, no means is provided for 
the determination of differential elevation (if any) to an intruder, as 
provided for by the present invention. While provision is made to activate 
a camera when an intruder is sensed, no means is provided for adjusting 
the focal length of the camera depending upon range to the intruder, nor 
for adjusting the angular elevation of the camera, as it is assumed that 
the intruder is on the same flat, essentially level surface as the robot. 
The present invention provides for camera focal length adjustment as well 
as azimuth adjustment, and further recognizes that differences in 
elevation between the installation and an intruder due to installation 
and/or terrain, result in a need to adjust the elevation of the camera for 
an accurate, relatively high resolution picture. Moreover, Maddox does not 
store a record of range information produced by the ultrasonic devices, as 
the Maddox robot is intended to be moving and thus any distances to other 
objects and ultrasonic reflections will always be changing. The present 
surveillance device is stationary, and accordingly "maps" of ultrasonic 
reflected distances are recorded and stored for comparison with those 
produced when the device is activated. 
U.S. Pat. No. 4,823,051 issued to William A. Young on Apr. 18, 1989 
discloses an Infrared Actuated Control Switch Assembly providing for the 
operation of an overhead light in a room. Two 360 degree conical viewing 
fields are provided for the detection of persons entering and remaining in 
a room. The passive infrared detectors of the present invention subtend a 
sufficiently broad vertical angle as to cover the required elevation range 
without need for two vertically spaced apart units or lenses. Moreover, 
the Young device seeks only to turn a light on or off, and thus no 
additional aiming apparatus or circuitry is needed, as in the present 
invention. As the Young device does not sense the specific direction of 
the heat source, it cannot provide for the aiming of a camera, as in the 
present invention. 
U.S. Pat. No. 4,890,093 issued to James R. Allison et al. on Dec. 26, 1989 
discloses a Solar Powered Proximity Triggered Light. No means is disclosed 
for the determination of a specific direction, distance or elevation of an 
intruder from the detector, and thus no camera is provided, as it would be 
impossible to aim such a camera properly without information pinpointing 
the location of the intruder. 
Finally, U.S. Pat. No. 4,896,039 issued to Jacob Fraden on Jan. 23, 1990 
discloses an Active Infrared Motion Detector And Method For Detecting 
Movement. As indicated by the Fraden '039 patent title, the device 
transmits an infrared signal at a temperature above ambient (i.e., shorter 
wavelength or higher frequency) and detects any reflected radiation in the 
transmitted wavelength. The infrared transmittal, and the additional 
energy required and possibility of detection by an intruder, are problems 
obviated by the passive nature of the present invention. Moreover, while 
means for intruder detection is disclosed, no means is provided for 
pinpointing the precise direction or azimuth of the intruder, nor the 
vertical elevation and range. Accordingly, no camera is disclosed, as the 
accurate aiming of such a camera is impossible without the ability to 
locate the intruder precisely. 
None of the above noted patents, taken either singly or in combination, are 
seen to disclose the specific arrangement of concepts disclosed by the 
present invention. 
SUMMARY OF THE INVENTION 
By the present invention, an improved interactive surveillance device is 
disclosed. 
Accordingly, one of the objects of the present invention is to provide an 
improved interactive surveillance device which may be used for a variety 
of purposes, such as surveillance of intruders and/or tracking an intruder 
with a camera and/or light. 
Another of the objects of the present invention is to provide an improved 
interactive surveillance device which utilizes a purely passive means of 
surveying the scanned area, and which activates an active transceiver to 
determine the range of an intruder precisely when an intruder is passively 
detected. 
Yet another of the objects of the present invention is to provide an 
improved interactive surveillance device which controls a camera, and 
provides for the precise control of azimuth, angular elevation, and focal 
length of the camera to provide a relatively high resolution picture of an 
intruder. 
Still another of the objects of the present invention is to provide an 
improved interactive surveillance device which does not require the 
intervention of a human operator. 
An additional object of the present invention is to provide an improved 
interactive surveillance device which includes a passive determination of 
the approximate size of an intruder, by means of the range determined by 
the transceiver, energy received by the passive devices, and appropriate 
microprocessor and/or computer programming. 
A further object of the present invention is to provide an improved 
interactive surveillance device which utilizes passive infrared detectors 
for continuous is surveillance of the subject area, and an ultrasonic 
transceiver for active determination of range, with the ultrasonic device 
remaining inactive until activated by the detection of an intruder by the 
passive infrared detectors. 
An additional object of the present invention is to provide an improved 
interactive surveillance device which is capable of scanning a field of at 
least 180 degrees of azimuth, and further precisely aiming a camera at an 
intruder within that field. 
Yet another object of the present invention is to provide an improved 
interactive surveillance device which is capable of operating in darkness 
and/or relatively low light conditions, by means of auxiliary lighting 
actuated by the device and/or an infrared or low light camera. 
Still another object of the present invention is to provide an improved 
interactive surveillance device which requires relatively little 
electrical power until activated by an intruder, due to the passive nature 
of the primary surveillance means. 
A final object of the present invention is to provide an improved 
interactive surveillance device for the purposes described which is 
inexpensive, dependable and fully effective in accomplishing its intended 
purpose. 
With these and other objects in view which will more readily appear as the 
nature of the invention is better understood, the invention consists in 
the novel combination and arrangement of parts hereinafter more fully 
described, illustrated and claimed with reference being made to the 
attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now particularly to FIG. 1 of the drawings, the present invention 
will be seen to relate to an automated interactive surveillance device 10, 
providing for the remote, automated surveillance of an area, e.g., 
automated bank teller machines, high security parking areas, unattended 
property, storage areas, and other areas which may be subject to vandalism 
or damage, etc. The primary sensing means of the present surveillance 
device 10 is an array of passive infrared detectors 12, hereinafter 
generally called. "PIRs" throughout the present specification. The PIRs 12 
are passive, in that they only receive energy, and do not transmit energy 
as an active device would which relies upon the reception of reflected 
energy from its own transmission (e.g., radar). Thus, the present 
surveillance device 10 cannot be detected by other devices which may 
receive transmitted energy, until the present device 10 has already been 
activated by an intruder as discussed further below. The passive nature of 
the present interactive surveillance device 10 also results in relatively 
low energy consumption until activated, as well as lower costs due to the 
lack of infrared transmission means required. 
The array of plural PIRs 12 is installed in a stationary base portion 14 
which may be permanently installed and immovably affixed to a stationary 
supporting structure, e. g., the building B of FIG. 1. A weather shelter 8 
or the like may be installed over the device 10 as desired, to provide 
some protection from the elements. While most of the components of the 
device 10 may be completely enclosed as they rely upon purely passive 
reception of energy and do not transmit, an ultrasonic rangefinder 
transceiver (described further below) is provided, and at least the 
transmitting antenna or orifice must be exposed. (Alternatively, other 
transceiver types may be used, e.g., microwave, etc.) The stationary base 
portion 14 serves as a base for a rotatable portion 16 disposed 
thereabove, as well as serving as a housing for other components of the 
device 10 described further below. 
The rotatable portion 16 is mounted on a substantially vertical rotary 
shaft 18 driven by a stepper motor 20 housed within the stationary base 
portion 14 (FIG. 2). A camera 22 (e. video camera, infrared camera or 
camera adapted to low light levels, or other camera as required) is 
mounted atop the rotary platform 16 by means of an arcuately pivotable 
camera mount 24 having a substantially horizontal pivot axis 26, thus 
enabling the camera 22 to travel in a vertical arc to adjust its angular 
elevation. The adjustment of the arcuate elevation of the camera 22 is 
provided by a pivotally mounted camera adjustment motor 28 (FIG. 2), which 
may drive a jack screw 30 or other means adapted to provide for the tilt 
or angular elevation adjustment of the camera 22. 
An ultrasonic rangefinder 32 is also affixed to the rotatable platform 16, 
preferably attached to the camera 22 so as to be automatically aimed in 
the same direction as the camera 22 at all times. Optionally, a light 34 
may be installed atop the rotary platform 16, preferably also affixed to 
the camera 22 and permanently aimed in the same direction as the camera 
lens. The camera 22, camera adjustment motor 28, and rangefinder 32 may 
communicate with the electronic circuitry housed within the stationary 
base portion 14 respectively by means of cables 36, 38, and 40. (Light 34, 
if so equipped, is also connected to the base portion by a power cable, 
not shown.) 
FIG. 3 provides a disclosure of the electronic circuitry contained within 
the stationary base portion 14 and providing for the operation of the 
present automated interactive surveillance device 10. In FIG. 3, eight 
different PIR circuits (for eight different PIRs), comprising a PIR 
circuit block 42, are disclosed. As noted above, the entire field scanned 
by the PIR array subtends 180 degrees horizontally; thus, each PIR of an 
array of eight PIRs will subtend a substantially equal horizontal field of 
22.5 degrees. The PIRs are installed within the stationary base portion 14 
of the device, behind a fresnel lens 48 (FIGS. 1 and 2) which provides a 
total of 180 degrees of coverage, and which serves to segregate the 
individual fields of view of each of the PIRs 12 by means of barriers (not 
shown, but disclosed in an earlier application by the present applicant). 
(The present surveillance device may be operable with as few as four PIRs, 
but directional sensitivity, and the resulting ability of the device to 
aim and adjust the focal length of a camera, will be somewhat less than 
with a greater number of PIRs each subtending a narrower field of view.) 
Each of the PIRs (such as the PIR 12 shown at the top of the PIR circuit 
block 42) communicates with a PIR circuit 44, each of which provides a 
signal to an amplifier circuit 46 (one of which is shown in PIR circuit 
no. 8 of the PIR circuit block 42). 
The signals from each of the PIRs 12 are supplied to an analog-to-digital 
(A/D) converter 50, which may be physically located with the 
microcontroller 52 of the device. (It will be understood that, as each of 
the PIR signals must be separated from every other PIR signal in order for 
the microcontroller 52 to determine which PIR(s) is/are being triggered, 
that the cable 54 from the PIR circuits to the A/D converter actually 
comprises a sufficient number of independent lines to provide separate 
signals from each PIR to a dedicated channel of the A/D converter. As an 
example, the eight PIR array shown in the drawing figures of the present 
surveillance device 10 provides signals to an eight channel A/D converter 
through eight separate lines between each of the PIRs and a corresponding 
A/D converter channel.) The microcontroller 52 in turn provides a signal 
to a sensitivity adjustment circuit 56, which circuit 56 provides 
adjustment to the PIRs 12 to preclude their being triggered or activated 
due to relatively small heat sources toward the range limits of the device 
10. 
Other input to the microcontroller 12 includes a camera height indicator 58 
comprising a plurality of switches, e.g., four switches in a four bit 
hexadecimal array. Thus, height indicator 58 could represent 16 different 
settings for heights from 0 to 15 feet in one foot increments (or 0 to 7.5 
feet in six inch increments, etc.). The microprocessor 52 reads the switch 
setting of the height indicator 58 and uses the height information to 
initialize a central tilt angle approximating aim at a target in the 
mid-range distance. This height information is also used in combination 
with range information provided by the transceiver 32, to determine the 
angle of tilt of the camera 22 to aim at a target within the field being 
surveyed, according to a trigonometric algorithm discussed below. Input to 
the microprocessor 52 is also provided by limit or "home" switches 60 for 
the platform stepper motor 20 and the camera tilt adjustment motor 28, 
which preclude motor operation past predetermined arcuate limits and 
reposition the camera and platform to a central position after actuation, 
and a photocell input 62 serving to disable the light 34 during daylight 
or relatively bright conditions. The microcontroller 52 also receives 
input from the receiver of the ultrasonic transceiver 32, after the 
transmitter portion has been activated by the microcontroller; the 
specific operation is described further below. 
Microcontroller 52 is programmed to provide output to control the platform 
motor 20 to position the rotatable platform 16 as required by means of a 
panning control circuit 64, and to provide output to a camera tilt control 
circuit 66 to position the camera 22 relative to the tilt angle. Once the 
camera 22 has been positioned, the microcontroller 52 will operate the 
camera by means of the camera control circuit 68, which circuit 68 turns 
the camera 22 on and off and controls the focal length of the zoom lens 70 
(FIGS. 1 and 2) as required. The microcontroller 52 also serves to actuate 
a video recorder when the camera 22 is actuated, by means of VCR control 
lines 72, to actuate the flood lamp or light 34 as required according to 
the signal received from the photocell 62 by means of a flood lamp relay 
74, and to provide a signal (video output, alarm, etc.) to a remote 
monitoring station by means of a communication port 76. 
FIG. 4 provides a software flow chart which describes the operation of the 
present interactive surveillance device 10. When the device 10 is 
installed, the camera height indicator 58 is initiated to provide the 
microprocessor 52 with the proper height above the ground or surface. The 
microprocessor 52 then actuates the platform stepper motor 20 to pan the 
camera 22, and particularly the ultrasonic transceiver 32 mounted thereon, 
to each of the zones established by the PIRs 12 of the PIR array in the 
stationary base portion 14 of the device 10. (The zones need not be 
limited to the number of PIRs in the array. The microprocessor 52 maybe 
programmed to recognize a situation in which two adjacent PIRs are 
detecting a signal and operate the stepper motor 20 to position the camera 
22 and ultrasonic transceiver 32 to an intermediate azimuthal position 
between the two adjacent PIRs. Accordingly, there will be seven 
intermediate zones interspersed between eight PIRs, or a total of fifteen 
positions to which the rotatable platform may be turned in the 180 degree 
semicircular field of azimuth of eight PIRs. Four PIRs will result in a 
total of seven positions.) The ultrasonic transceiver 32 is then activated 
at each of the PIR zones (and/or intermediate points), and an "object 
table" of the distances measured by the ultrasonic device 32 is recorded 
and stored in the object table memory 78 (FIG. 3). The camera 22 and video 
recorder are not activated at this time, as the device 10 is merely 
"surveying" the area to establish a standard background. This step is 
repeated from time to time, according to the microprocessor programming, 
when the PIRs are not detecting any significant infrared radiation. 
When one (or two adjacent) PIRs 12 receive a higher than normal amount of 
infrared radiation, its/their output is sent to the microcontroller 52 via 
the cable 54 and A/D converter 50. The microcontroller 52 then compares 
the signal intensity received with background, and actuates the camera pan 
control circuit 64 to cause the stepper motor 20 to turn the rotatable 
platform 16, and camera 22 and ultrasonic rangefinder or transceiver 32, 
to align them in the direction of the activated PIR(s). The camera tilt 
control circuitry 66 is also operated to position the vertical angle of 
the camera 22 at a midpoint of its arcuate vertical travel (if not already 
so positioned), as the exact distance of the intruder detected by the PIRs 
is not yet known. The ultrasonic transceiver 32 is then activated to 
provide a new ultrasonic "map" of the area, which is compared with the 
same ultrasonic "map" previously stored in the object table memory 78 and 
formed during a period of PIR inactivity. 
If the two ultrasonic ranges or "maps" show substantial correspondence, and 
thus no ultrasonic return from an intruder, then the microprocessor 52 
treats the PIR activity as a false alarm due to random heating of the 
environment (e.g., clouds/sunlight, reflections from pavement or another 
building or window, etc.), and the rotatable platform 16 is returned to a 
central position for future operation. However, in the event that the new 
ultrasonic "map" fails to agree substantially with the base "map" data, an 
intruder is indicated, and the microprocessor 52 will activate the camera 
22 (and light 34, depending upon the available light as determined by the 
photocell 62) and operate the camera tilt motor 28 and adjust the focal 
length of the zoom lens 70 according to the distance determined by the 
ultrasonic rangefinder 32 and the height of the camera established by the 
height indicator 58, to provide a relatively narrow field, high resolution 
view of the intruder. A video recorder is also activated by means of VCR 
control lines 72, and a signal may be provided to a remote post via the 
communication port 76 and communication/power cable 80 (FIGS. 1 and 2). 
As an example of the above, let us assume that the lens 70 of the camera 12 
is positioned fifteen feet above the surface, measured at the base of the 
building B to which the present surveillance device 10 is mounted. The 
platform 16, camera 12, and rangefinder 32 are turned to provide an 
ultrasonic range to an intruder, and the range is determined to be fifty 
feet; the face of the intruder is initially assumed to be approximately 
five feet above the surface. Assuming the ground to be level, it will be 
seen that the fifty foot distance from rangefinder to intruder comprises 
the hypotenuse of a right triangle, with the ten foot height of the camera 
above the face of the intruder forming the adjacent side. The 
microprocessor 52 may be programmed to calculate the resulting angle of 
depression or tilt angle for camera 22, by means of relatively simple 
trigonometric functions, i.e., dividing the height of the camera by the 
distance established by the rangefinder to establish the cosine of the 
complementary angle to the angle of depression (cos 10/50=0.200=approx. 
78.4 degrees) and subtracting that angle from 90 degrees to arrive at the 
correct angle of depression of approximately 11.6 degrees. (It will be 
seen that with further programming of the microcontroller 52, more complex 
terrain conditions may be taken into account, e.g., a slope toward or away 
from the building B upon which the present surveillance device 10 is 
mounted, or conditions of uneven terrain in different directions from the 
device 10.) 
The above surveillance device 10 and programming therefor may be further 
refined by comparing the infrared signal intensity received by the 
activated PIR(s) to the intruder distance measured by the ultrasonic 
rangefinder 32. A "map" of representative infrared intensities of 
representative size ranges of people may be programmed into the 
microprocessor 52, which may be compared with the distance established by 
the rangefinder 32. If the infrared intensity is greater (or less) than 
that of a person of standard size, the angle of depression of the camera 
22 may be adjusted slightly upwardly (or downwardly) in order to "fine 
tune" the vertical tilt or aim of the camera to provide a more accurate 
view of the head and upper body of the intruder. 
An intruder thus discovered may be viewed for a predetermined amount of 
time, or the camera and video operation may continue as long as the 
ultrasonic rangefinder continues to report an intruder in the given 
direction towards which the rangefinder is pointed and the appropriate 
PIRs continue to indicate a non-standard infrared signature. When the 
intrusion threat has ended (by having infrared and ultrasonic indications 
return to normal, and/or security personnel taking action, etc.), the 
microprocessor will shut down operation of the ultrasonic transducer, 
camera, video recorder, and light (if used), and return the platform 
position and tilt angle of the camera to substantially central positions, 
where they can be moved relatively rapidly in either direction of travel 
should another threat arise. 
The above described interactive surveillance device 10 will be seen to 
require no external monitoring, and is completely passive in its operation 
and transmits no signal or energy until the passive infrared detector(s) 
is/are triggered. The device is interactive with an intruder, in that as 
an intruder moves laterally, he/she will trigger other PIRs, which will 
cause the microprocessor to change the azimuth of the camera (and 
ultrasonic transreceiver) accordingly to continue to track (and provide a 
video of) the intruder. The device serves as an extremely cost effective 
means of monitoring virtually any critical area where it is impractical to 
position a security guard at all times. 
It is to be understood that the present invention is not limited to the 
sole embodiment described above, but encompasses any and all embodiments 
within the scope of the following claims.