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.
- A. The Camera
- 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.
- B. The Monitor
- 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).
- C. The Cable
- 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.
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).
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.
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:
Manual Passive
Switchers
Homing Sequential
Switchers
Bridging
Sequential Switchers
Alarm Programming
Sequential Switchers
For your convenience,
a simplified description of each of the four basic switcher types is
described below:
Manual Passive
Switchers
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.
Homing Sequential
Switchers
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.
Bridging Sequential
Switchers
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.
Alarm Programmed
Sequential Switchers
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).
The lens will determine
the area viewed by the camera and help the camera adjust to varying
light conditions.
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.
Housings protect
the camera from environmental conditions and vandalism or conceal it
from the public.
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.
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 |
|
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.
Mount Types
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.
Weight Load
- Add
together the weights of all the units affixed to the mount.
Wall, Ceiling,
Pedestal - 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.
Adjustable Heads
- Adjustable
heads are available on most mounts to provide vertical as well as horizontal
adjustment of camera position.
Supplemental
Components
Video Cassette
Recorders - 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.
Video Motion Detector
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.
Inserter/Splitter/Picture-in-Picture
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.
RF Modulator
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
|