CCTV Information
Introduction
Designing CCTV security systems is quite
simply a matter of putting together a number of components. You don't need
a technical background or even a very comprehensive knowledge of how each
of the components operate. But you do need to know what each component
does and what its requirement is.
In this guide, we will describe most
of the common closed circuit television components and supplementary equipment,
and provide guidelines for their selection.
Basic CCTV Components
The three basic components of all CCTV
security systems are the camera, the monitor, and the cable. While other
supplemental components may be added into more complex systems, the camera,
monitor and video cable form the core of all CCTV security systems.
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A. The Camera
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The camera is the eye of the system. Its
only function is to provide a view of the site under surveillance by sending
an electronic signal along a video cable. It is passive, it only views
the scene similar to the human eye.
Tube cameras are no longer used for
a few reasons. Tubes wear out, are fragile, more expensive, and cannot
match the versatility of the CCD (Charged Coupled Device or 'chip') camera.
At Rayco Security, all of the cameras
installed are CCD cameras. To date, not one camera has needed replacement
due to worn out parts, degraded video output, or any other defect in the
camera itself.
Our return service on a completed install
is .5% to 1% annually. This is due to quality equipment, proper placement,
and a well trained sales and technical staff.
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B. The Monitor
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The monitor receives the signal sent by
the camera and converts the signal into a picture on a television screen.
At least one monitor must be provided at each viewing station in the CCTV
system in order to see the view provided by the camera(s).
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C. The Cable
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The cable required for a basic system is
75 ohm coax cable. RG59U is the normal coaxial cable used, this cable must
be copper center conductor and 95% shield.
Each camera is connected by an individual
cable to a switcher, and only one cable runs from the switcher to the monitor.
This is because only one video signal can be transmitted on any monitor
at any one time. The viewer uses the switcher to determine which camera's
video signal will be sent onto the monitor and displayed on the screen.
The viewer may make the selection manually or program a sequential switcher
to automatically change from view to view.
In security CCTV systems with a large
number of cameras, it is usually desirable to divide the cameras into groups
and use a second switcher and a second monitor to provide views of the
different areas.
How To Select The Basic Components
A. Cameras
The first criteria for selecting a camera
for a CCTV system is the minimum light level the camera must operate in.
This criteria remains constant regardless of whether the camera is mounted
indoors or outdoors.
CCD cameras can be divided into three
classifications of operation based on lighting considerations. These three
classifications are listed with descriptions of the levels of light.
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General Purpose Cameras - Most general
purpose cameras will work well indoors. Light levels must remain relatively
high and evenly illuminated to effect a good quality picture. (With out
the aid of auto-iris lenses or infrared illumination).
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Low Lux Cameras - A low lux camera can
in some instances 'see' with the illumination from a single lit match.
In reality, CCD cameras see well in the infrared spectrum. A low lux camera
is any camera with a lux(level of light measurement) below 1 lux. A lux
of .5 is near total blackness to the human eye, yet to some CCD cameras
it looks an overcast day. These low lux cameras are ALWAYS black and white
output.
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Color Cameras -Color cameras require an
enormous amount of light compared to a black and white camera. A color
camera would work well indoors with bright illumination. Outdoors, high
intensity lights(75 to 150 watts) would be needed at night to reflect the
colors back on to the camera. Daytime light usually is adequate for a color
camera.
B. Monitors
Selection and placement of monitors is
quite simple, but very important. The only decision is which size to use,
and that is determined by the viewing distance. The table below provides
a reference for determining appropriate monitor sizes:
Viewing Distance |
Recommended Monitor Size |
Recommended Monitor Size |
14" - 36" |
9" |
9" |
36" - 50" |
12" |
12" |
50" - 76" |
15" |
19" |
C. Switchers
There are four basic categories of switchers:
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Manual Passive Switchers
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Homing Sequential Switchers
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Bridging Sequential Switchers
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Alarm Programming Sequential Switchers
For your convenience, a simplified description
of each of the four basic switcher types is described below:
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Manual Passive Switchers
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Manual passive switchers are the most economical
way of connecting two or more cameras to a single monitor. The user changes
from camera to camera by pushing a simple mechanical switch on the front
of the switcher.
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Homing Sequential Switchers
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Homing sequential switchers can be set
up to automatically switch from camera to camera. The amount of time each
view stays on the monitor screen can be varied from 3 to 45 seconds. Once
the cycling time has been established, any of the cameras can be either
eliminated from the sequence or selected for extended viewing with the
flip of a switch. Returning the switch to its normal position will include
that camera in the program and start the cycle all over again. Homing sequential
switchers can be homing, homing bridging, homing looping, and looping bridging.
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Bridging Sequential Switchers
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Bridging sequential switchers operate the
same as the homing sequential switcher, but provide an outlet for one additional
monitor. One is used to display any of the selected camera views while
the second monitor provides the sequence of the cameras, allowing extended
viewing of one special scene while continuing to display all scenes.
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Alarm Programmed Sequential Switchers
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Alarmed programmed sequential switchers
perform like the above switcher but include one set of terminals for each
camera position to call up that position by use of magnetic contacts, video
motion detectors, or conventional motion detectors. Primarily used in conjunction
with video cassette recording.
Camera-Related Equipment
For each camera in the system, there are
four determinations to be made after you have selected the camera (by its
operating light range and power supply).
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The lens will determine the area viewed
by the camera and help the camera adjust to varying light conditions.
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Pan/tilts and scanners can provide greater
coverage of an area with a single camera by moving the camera from side
to side and up and down.
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Housings protect the camera from environmental
conditions and vandalism or conceal it from the public.
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Mounts are required to place the camera
in its intended location.
Lenses
How much of an area is "seen" and transmitted
by a camera is determined by the focal length of the lens and whether or
not it has a zoom function. Cameras operating in very low light conditions
will may require auto iris and/or spot filtering to operate properly. Some
newer CCD cameras have an electronic iris feature that allows a larger
light range with out the use of auto-iris lenses.
Focal Length
The focal length of the lens determines
the field-of-view of the camera. Short focal length lenses (low numbers)
have a wide field of view and display more of the scene. Long focal length
lenses (high numbers have a telephoto effect and provide more detailed
views of distant targets.
NOTE: Increasing the monitor size does
not increase the clarity of the image, it just enlarges the picture. If
you need a good clear view of distant detail, you must use a lens selected
for the specific application.
When selecting the field-of-view, a
good rule of thumb is that 25% of the monitor height is a minimum for good
identification of a person. The most direct way of determining the appropriate
focal length (field-of-view) is to use a manual wide range zoom lens on
a test camera at the intended site, as follows:
With the test camera in the selected
location, run through the zoom range until the desired view is obtained.
Then simply read the indicated focal length off the zoom lens.
The best means of calculating the required
lens focal length without an actual test employs a lens selector guide
supplied by several manufacturers.
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Note 1:
As mentioned before, every CCTV system
should be viewed with a test camera, test lens, and test monitor at the
job site prior to a fixed price or firm quotation. Only if your customer
can actually see the picture before he buys can you be sure they'll be
entirely satisfied. A selection of lenses from the following chart or from
your own graphs are approximations at most. The margin for error is high.
Fixed Focal Length Lenses Fixed focal length
lenses have a permanent field-of-view. They are the most economical lenses
available and are used in most general surveillance situations.
Angular Field-of-View (Approximate)
2/3" Format
Focal Length |
Horizontal Field of View |
4.0 mm |
95 degrees |
4.5 mm |
88 degrees |
4.8 mm |
85 degrees |
6.0 mm |
72 degrees |
8.0 mm |
57 degrees |
9.0 mm |
52 degrees |
10 mm |
47 degrees |
16 mm |
30 degrees |
135 mm |
14 degrees |
|
1" Format on 2/3" Format
Focal Length |
Horizontal Field of View |
5.5 mm |
76 degrees |
6.5 mm |
68 degrees |
8.0 mm |
57 degrees |
12.5 mm |
38 degrees |
25 mm |
19 degrees |
40 mm |
16 degrees |
50 mm |
10 degrees |
75 mm |
6 degrees |
135 mm |
3 degrees |
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Zoom Lenses
Manual zoom lenses with the field of view
variable by hand at the camera location.
Motorized zoom lenses with the field
of view controlled by the viewer at the monitor (remote) location. Manual
zoom lenses are rarely used in security application since camera access
is generally impractical. Motorized zoom lenses are very effective for
panoramic surveillance of an area with the capability of close inspection
and identification of a person or object in the scene.
Iris control
The iris is a variable opening in the lens
which can be closed down to limit the amount of light entering the camera.
Most low light level cameras require lenses with automatic iris control
. Auto-iris lenses are electronically controlled by the camera, but can
be overridden with remote controls at the monitor location.
Spot Filter
A spot filter is an area in the center
of the lens which greatly reduces the amount of light passing through it.
When the iris is wide open, it has very little effect, but as the iris
closes down, the spot filter occupies more and more of the open area and
provides more filtration of light to the limits required by the tube. Spot
filter lenses are only used with iris controls for low light level cameras.
Voltage
The performance of 115VAC and 24VAC units
is identical. The deciding factor is the cost of the power supply wiring.
115VAC units can use low gauge wire for very long distances, but conduit
may be required by local ordinance or electrical code. 24VAC units require
heavier gauge wiring, but conduit is not normally required.
Relay boxes allow the use of lighter
gauge wire with 24VAC controls, 115VAC is required at or near the camera
location.
See RCA/Panasonic data sheets for wiring
requirements of individual units.
Auto-Scan
The auto-scan feature on pan & tilt
units provides automatic horizontal sweeping of the camera to predetermined
limits. The automatic control can be overridden to stop at any position
or for manual control of the sweep. Use in the auto-pan mode is discouraged
for outdoor applications and/or variable light conditions.
Accessories/Options
Variable speed in both pan and tilt functions
Explosion proof
Cable guards to reduce cable wear and
prevent tangles
Preset position
Housings
If the camera location is indoors, a housing
is usually required only to protect the camera from vandalism or to conceal
it from view in a decorative globe unit . For outdoor installation, the
addition of environmental accessories is required. The outdoor housing
accessories are described below - the preceding reference chart is included
showing available accessory features.
Accessories for Outdoor Housings
Heater: Protects down to -10 degrees Fahrenheit.
Available in 115VAC & 24VAC models.
Extreme Low Temperature Package: Protects
down to -80 degrees Fahrenheit.
Blower: Protects at temperatures above
90 degrees F. Available in 115VAC & 24VAC models.
Sunshield: Overall shade for high temperature
protection.
Insulation: For both hot and cold environments.
Window Wiper: With and without washer
to clean the window.
Controls: For all functions, can be
operated from monitor area.
Mounts
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Type
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The unit mounting plate on each type of
mount has a different bolt pattern to facilitate the unit. Cameras and
housings can be mounted directly to pan & tilt or scanner units, which
in turn require mounts for installation.
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Weight Load
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Add together the weights of all the units
affixed to the mount.
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Wall, Ceiling, Pedestal
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Wall and ceiling mounts are recommended
for indoor use, pedestal mounts for outdoor use. The clearance required
by the mounted unit is the determining factor in selection.
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Adjustable Heads
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Adjustable heads are available on most
mounts to provide vertical as well as horizontal adjustment of camera position.
Supplemental Components
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Video Cassette Recorders
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The addition of a video cassette recorder
in CCTV systems adds a great deal of flexibility. It can be used to review
the activities of the day or week, provide a visual record of all transactions,
and provide unattended surveillance during non-business hours, although
apprehension would not be a function of the system.
A built-in time/date generator imprints
the time and date on every scene for reference. For time lapse recording,
the unit can be set to extend to two hour cassette tapes to up to 999 hours
of surveillance by recording only at preset intervals. It can also be set
up to respond to an intrusion by converting back to real time recording
(no time lapse between recorded images), sounding an alarm and triggering
any other alarm system or device.
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Video Motion Detector
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The video motion detector is a silent guard
that can watch over a sensitive or vulnerable area in a building, such
as a safe. When no employees are present, it maintains a constant vigil
over the designated area, while rejecting certain types of false alarms.
It can be integrated into a system to alert a video cassette recorder of
an intrusion or initiate an alarm situation with other alarm devices. The
primary detector requires a change in the video signal caused by light
change. A constant stable lighted area is required.
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Inserter/Splitter/Picture-in-Picture
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This component splits the screen on a single
monitor to accommodate pictures from two separate cameras simultaneously.
This would work well if a store manager wishes to check on employees ringing
up purchases on a cash register. By placing one camera with a narrow focal
width on the cash register and a second camera with a wider focus on the
counter, he is able to identify the merchandise and the price being rung
up. If he doesn't have time to watch it during the day, he can include
a video cassette recorder into the system and record the days' activity
for review at a later date. Note: A splitter does not compress the whole
picture into half the monitor - it only displays one-half the area being
viewed. This device works best as a scene inserter as opposed to a splitter.
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RF Modulator
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Cameras send out their picture as a video
signal (voltage). This signal can only be read by equipment designed to
accept a video signal, such as monitors, switchers, and VCR's, etc. An
RF modulator adapts the CCTV security camera signal for display on a standard
home TV set. For example, in a condominium or apartment complex with a
security gate or lobby, when someone comes to the gate and rings a tenant
on an intercom, the tenant could view the visitor on his TV set on an unused
channel assigned to the camera before answering the intercom.
Shared System
Any of the individual camera views may
be viewed independently or included in the automatic program at either
station. It also provides independent viewing at two separate locations.
Partially Shared System
Some of the camera views are available
only to a single station. Some of the camera views are shared.
Bridging System
An automatic program on monitor
1 can be bridged onto a separate viewing station. Selected views may be
held on monitor 1 without interrupting the automatic program on monitor
2.
How To Select The Video Switcher
Introduction
The broad range of video switching equipment
currently available allows us to create closed circuit television systems
to individualized needs with standard, off-the-shelf components. Unfortunately,
the large variety of equipment has produced some accompanying confusion
regarding its use.
Probably the most common misunderstood
component in a CCTV system is the video switcher. This is particularly
regrettable since the efficiency of the entire system is directly dependent
on proper application of the correct switcher.
In an effort to provide a better understanding,
we will examine here the basic switcher types and what functions they can
provide in a CCTV system. Beginning with the most basic mechanical switcher
and progressing through the sophisticated models, we will present each
in a hypothetical system and consider how it will satisfy the requirements
of an imaginary company.
We will start our company (and our system)
very simple requirements. One of the executives (Mr. Smart) needs to occasionally
view - without leaving his office - any or all of four nearby area: the
front lobby, the production area, the shipping/receiving area, and the
warehouse. Obviously, he will need four cameras, one for each location.
And since he is the only one with viewing requirements, he will need only
one monitor in his office. He will also need some means of selecting which
video input will be displayed on his monitor at any given time. Mr. Smart
needs a video switcher.
Choosing A Video Switcher
All switchers have a common basic function
- they are used to determine which of the input signals will be taken off
ground termination and applied to the output line - in this case, his monitor.
At present, Mr. Smart's budget is the
most pressing concern, so we will provide him with the lowest price switcher
available.
Manual Passive Switcher
A manual passive switcher will suit his
modest requirements quote adequately. Like all switchers, it functions
as a multiple-choice splice between input and outputs, in this case with
the selection made manually. As the term "passive" suggests, this switcher
contains no electronically active components. It merely allows Mr. Smart
to select which of the available inputs he wants displayed on his monitor,
and completes the appropriate circuit by mechanical means.
In using a passive switcher, Mr. Smart
will have to put up with a few inconveniences. The force required to operate
the mechanical switches will probably be just enough to require him to
use his other hand to hold the desktop unit in place. Without benefit of
internal electronics, switching to a new camera input will produce spikes,
flashes, and a temporarily garbled image, which will take a second to clear.
Occasional maintenance will be required to clean the mechanical switches.
If these minor annoyances are of no
great concern to our Mr. Smart, he should be satisfied with a manual passive
switcher.
Manual Active Switcher
But suppose he isn't satisfied. Let's make
our Mr. Smart a little more exacting. He can't afford the down time for
maintenance. When he switches from the warehouse to shipping/receiving
he wants to see a clear image immediately, and he's constantly on the phone
so he needs feather-touch switching capability.
A manual active switcher should fill
the bill. The electronic analog switch is activated by a feather-touch
switch. internal circuitry, with vertical interval switching capability,
provides instantaneous switching with no visual disturbances.
With a manual active switcher, Mr. Smart
has eliminated the technical inconvenience of his previous passive switcher,
but he still must make each video selection by hand. That may be all right
for now, but let's increase his requirements and see what we can do for
him. We'll assume he still has the same four areas to monitor, but now
needs to check them more frequently.
Sequential Switcher
Now he needs someone or something to switch
from camera to camera for him so that he can keep an eye on what's going
on all over the plant with just an occasional glance at his single monitor.
A sequential switcher will do just that
for him. Basically, an automatic active switcher can be programmed to progress
from input to input, displaying each area in turn on the monitor in an
indefinitely repeated cycle. Like the previous manual active switcher,
it contains electronic circuitry to provide fast, clean switching, but
it also provides the decided advantage of automatic switching. Of the wide
variety of sequential switchers available, let's start our Mr. Smart out
with the simplest and see what new capabilities it provides.
Homing Sequential Switcher
A homing sequential switcher will allow
Mr. Smart to view each of the areas, one through four, in repeated sequence
by simply turning the switcher on. He can vary the dwell time of each individual
camera from 1 to 45 seconds. Thus, his programmed sequence could be camera
one (of fleeting interest) for one second, camera two (more to see) for
a full 30 seconds. In this configuration, the four (of moderate importance)
will show for 15 seconds each. The switcher will automatically sequence
through positions one through four, displaying each area for the allotted
time and repeating the program every 61 seconds. Not all homing sequential
switchers provide an adjustment for each input. Some provide one adjustment
only, which means if the setting is 10 seconds that each camera scene will
be displayed on the monitor for 10 seconds.
Once the standard program has been established,
it can be extended over a sliding range up to twice the original dwell
time settings. Thus, with a simple control knob, the sequencing can be
slowed to up to 180 seconds, or double the individual dwell time settings.
Sometimes, however, the program requirements
may call for the elimination of one of the cameras from the sequence. If
Mr. Smart is overseeing the flow of materials from warehouse to production
to shipping for a rush job, he probably doesn't care who is in the front
lobby and may find it disturbing to have the view in his automatic sequence.
If so, he can temporarily eliminate camera one from the program by simply
moving the position switch on the unit to bypass. Thus, the sequence will
now be two, three, four, two, three, four, etc., skipping number one until
Mr. Smart decides he wants the lobby view back in the sequence and returns
station 1 to automatic.
Suppose now a problem develops in the
production area requiring Mr. Smart's full attention. By changing the switch
for position two to select (or home), he can keep camera 2 input on the
screen and temporarily override the sequential switcher like a manual switcher
controlling which input is displayed by returning the previously selected
switch to automatic (or bypass) and changing the appropriate switch to
select.
Whenever he wishes, he can return to
his standard sequencing program by simply returning all switch positions
to automatic. The switcher will start all over again, progressing from
one to two to three to four and back to one again, all to his original
timing.
The homing sequential switcher provides
Mr. Smart with a number of operational options, such as automatic switching,
timing and bypass control, and individual hold of any of the available
inputs. In the automatic switching mode, each of the four monitored areas
will be displayed at preselected intervals, so he can keep abreast of what
is happening all throughout the plant by merely glancing at the screen
occasionally. If he sees something of concern to him, he can home in on
it by putting the appropriate switch on select, thereby holding that single
input on the screen in lieu of the programmed sequence.
Now, let's suppose Mr. Smart would like
to have his cake and eat it too, so to speak. He wants to select individual
views for extended study, but does not want to give up the constantly updated
preview provided by the automatic sequence. We can give him that capability
with a single switcher.
Bridging Sequential Switcher
A bridging sequential switcher is a sequential
switcher with separate outputs for two monitors, one for the programmed
sequence and the second for extended display of a single area. Unlike the
homing sequential switcher the bridging sequential switcher provides this
constant viewing of a selected input without giving up the overview of
all areas provided by the sequential program.
With a bridging sequential switcher,
when Mr. Smart wants to observe a particular area in detail changing that
station to select will complete a circuit to monitor two, causing that
input to remain in view indefinitely. Meanwhile, monitor one will continue
uninterrupted with the original program sequence, including the view selected
for independent viewing.
If Mr. Smart has security responsibility,
he can record the selected image from monitor two output while keeping
an eye on all the other areas for further developments.
VCR/Homing Sequential Switcher
On the topic of security, Mr. Smart has
an important question: "Is there any way my system could be utilized when
no one is there?" A welcome question, especially when we have two excellent
answers.
One solution, of course, is to include
a time lapse video cassette recorder in his system for use when the plant
is unoccupied. For unattended surveillance, a time lapse VCR/homing sequential
switcher system can be left on overnight or over the weekend. The switcher
will continue through four, in sequence on the monitor, but the time lapse
VCR will only record one out of every 6, 13, 25 or 38 frames, depending
on which mode it is set in. Thus, when played back at normal speed, up
to 72 hours of surveillance can be reviewed in 120 minutes of viewing (24
minutes at first playback).
But suppose even that's not enough for
our Mr. Smart. What if he wants an extended look at any intrusion, recorded
in real time? He needs a switcher that will respond directly to the intrusion
itself, an auto alarming switcher.
Auto Alarm Sequential Switchers
Auto alarming sequential switchers come
in either the one monitor homing format, or the two monitor bridging format.
In either case, they can be triggered by a variety of sensing devices.
Magnetic contacts, pressure sensitive floor mats, window foil stripping,
motion sensors, and other intruder/detection devices can be connected directly
to the switcher from any or all of the areas under camera surveillance.
First, let's equip our Mr. Smart with
an auto alarming homing sequential switcher with the alarm turned on. The
system will function exactly like the homing sequential switchers described
above, until there is an intrusion.
In conclusion, Get Smart, Get Safe and
Get RAYCO |