Security Labs SL611 Manual de usuario descargar pdf (Pagina 11)

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cctv reference guide

Surveillance recorders & digital technology

Why Digital?

During the last decade, microprocessor based (digital) technology

has made major advances. Processors, hard drives, and

computer memory are continuing to increase in speed and ability.

In the surveillance industry, these advances have made it

possible for recording digital video. A Digital Video Recorder

(DVR) retrieves the video from a security camera, multiplexer, or

other source, and converts the signal from analog to digital. The

digitized video data is then compressed and stored on the DVR’s

hard drive. Video compression (making

the data size smaller) allows the

digitized video to be stored

efficiently. The process of storing the

video data on the DVR hard drive is

similar to the way your desk top

computer stores a word processor or other data

file. The file (video image) is ‘marked’ when stored so the user

has quick access to it at a later time. Because the DVR operates

like a computer, retrieval of data (video) is very fast. A search by

event, time and date, or by camera, happens almost

instantaneously. The resolution (image size) and quality (amount

of compression) are features that can be set by the user and

determine how large and how detailed the playback image is on

the monitor. Setting the image for full screen playback with

optimum detail requires the most data space on the hard drive

and will lower the number of hours of video that can be stored

before the hard drive is full. An “overwrite when full” feature

assures the user that should the hard drive become full, the DVR

will continue to record by writing over the oldest video first. Like

time lapse recorders, DVRs can be set to record at different frame

rates. The fastest any DVR or time lapse can record is 60 fields

(images) per second. Setting the recorder to a much slower

setting, for example, one image every 8

seconds, will greatly extend the

total recording time. Like time

lapse recorders, DVRs can

also be set to event record

when triggered by an external

trigger such as a door contact,

or by a preprogrammed

schedule. Adjusting the DVR for

the appropriate frame rate, image size, and

compression is simplified with on screen menus. Advanced

features (some models) allow you to connect to the DVR though

the TCP/IP protocol in your desktop or laptop computer. The DVR

can be connected to your office’s local area network (LAN) and

cameras can be viewed at your PC monitor. If your LAN is

connected to a broadband internet connection (DSL or cable), the

DVR connected to the LAN can be viewed from home via the

internet.

How does IR Work?

The human eye can see in the visible light portion of the spectrum

chart (above). Above visible light is infrared (IR). The CCD or

CMOS device inside your security camera can detect IR light and

use it to help illuminate the area viewed. Many Security Labs

cameras emit IR so that the area in front of the camera can be

seen in total darkness. ONLY black and white (B/W) cameras

are affected by IR illumination. Color cameras will detect IR to a

much lesser degree. Take your TV remote and press a button

while pointing it at your camera for a simple demonstration of how

a CCTV camera can see IR.

How much will the security camera see?

The field of view (FOV) is based on the camera & lens. Security

Labs cameras are supplied with a wide angle view lens. Wide

angle lenses are suitable for most applications due to their ability

to view a large area. A 4mm wide angle lens will be able to view

an area 20’ high x 26’ wide at 21’ away. As an example, a 15’ x

15’ room is shown in the diagram below. Observe that the 4mm

lens (green arrows) allows better wide angle viewing coverage

than the 12mm lens (red arrows).

Why choose an 8 or 12mm lens?

In applications where a closer view is needed (such as above a

cash register or over a greater distance), an 8 or 12mm may be

desired. The same camera (above) at 21’ away with a 8mm lens

will have a 10’ vertical x 13’ horizontal FOV. At 21’ with a 12mm

lens, the FOV will be approx 6’ vertical x 9’ horizontal. Increasing

the focal length of the lens decreases the perceived distance to

the viewing area. The SLC-110, SLC115, SLC-120, and SLC-

1041 cameras have interchangeable lenses available in 8 and

12mm.

How does a time lapse recorder work?

A Security Labs time lapse is set up in a very similar fashion to

your home VCR. It is very simple to connect and operate!

Time lapse recorders, as their name implies, slow down the

recording process and create a time lapse between recorded

frames. The purpose behind having lapses between recording

intervals is to increase the amount of recording time on an

individual tape. Unlike a standard VCR which has a maximum

record time of 8 hours, time lapse recorders (such as the Security

Labs SL811) can record from 2 to 960 hours (15 selectable record

speeds) on one standard VHS tape. With a time lapse recorder,

one can be assured that his or her property has active

surveillance recording around the clock. The playback of a

Security Labs time lapse will always have a clear, noise free, high

resolution picture. The table below demonstrates the increased

time between images in extended record speeds.

2 Hour 1/60 second Yes

6 Hour 1/60 Yes

18 Hour 1/20 Yes

24 Hour .22 No

36 Hour .32 No

48 Hour .42 No

72 Hour .62 No

96 Hour .82 No

120 Hour 1.02 No

168 Hour 1.42 No

240 Hour 2.02 No

360 Hour 3.02 No

480 Hour 4.02 No

720 Hour 6.02 No

960 Hour 8.02 No

RECORD TIME BETWEEN AUDIO

SPEED RECORDED IMAGES RECORDING

See LENSES on page 8 for a chart on your specific FOV

Approx. field of view (FOV)

with Security Labs cameras

SLD230M Compact DVR

SLD240 DVR with LAN

15 feet

CAMERA

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Security Labs SL611 Manual de usuario Pagina 11

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