Specifications

Security 2009
KNOW-HOW: Digital Recording
S10
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Digital Recording
Many years ago, analog timelapse recorders have dominated the
market of video recorders. Although, these systems were of low cost
when purchasing them, regular maintenance work, e.g. the replace-
ment of the video head disk and other mechanical wear parts, were
expensive.
Today, the emphasis is placed on digital recorders which store their in-
formation mainly on hard disks. This has been made possible by the ex-
tending capabilities of computer technologies. The application of these
technologies allows to manufacture units with versatile features and
power capabilities which were so far only known by using many dif-
ferent individual units. The result of this is that certain types of units have
almost completely vanished from the market.
External multiplexers, for example, are hardly available on the
market anymore, because they are already integrated in the recorders.
Today DVRs are available in various housing designs with versatile
features.
Multichannel units
These types of units are supplied ready for operation, i.e. only the mere
configuration must be carried out. These recorders are equipped with
all the necessary connections for video signals and alarm signals. The
special Linux operating system allows for a reliable operation which is
also obtained by matching hardware components in such a way that
an operation around the clock is possible without any problems. The
latest DVRs operate without a fan and allow an application also in
quiet office surroundings.
Advantages of ready-to-use units:
– ready for operation straightaway
– no assembly necessary
– compact design
– operational controls are functional
– effective power supply
The abbreviation of these systems is DVR and they are available in dif-
ferent sizes and performance classes. Units with 4, 9, or 16 camera in-
puts are commonly used.
One-channel recorders
The DVR-100H represents a certain special form. It was designed as
a direct replacement for analog tape recorders. With this unit, existing
systems can also be updated with new technology at a favourable
price. In this case, the DVR-100H replaces the existing analog time-
lapse recorder. The operation and programming is very close to exist-
ing analog units. The one-channel DVRs usually do not feature motion
detection as opposed to multichannel DVRs.
Insert cards
Insert cards for the PC are also popular. These cards allow Windows-
based PCs to become very efficient DVRs. At these systems, the com-
plete hardware installation and software installation must be carried
out by the customer prior to setting the unit into operation. The min. sys-
tem requirements on the PC hardware must at least be met in order to
obtain the max. power capacity, but it is usually advantageous if they
are above it. This type of DVR should not additionally be used as an
ordinary office computer to ensure an operation on a windows oper-
ating system as secure and with as little interference as possible. A
good knowledge of operating systems and hardware configuration is
essential for the application of these card systems because many PC
components must be interconnected.
Mini digital recorders
With these units the dimensions are tried to be kept as small as pos-
sible. These units are partly only the size of a small plate and the
recording is often stored on a solid-state memory, e.g. SD or CF cards.
These recorders are mainly used for a concealed surveillance.
Current DVRs combine a variety of functions in one housing which
were previously only possible by using separate special units. To name
all the function and characteristics in this case would be too extensive,
therefore we only describe the most important ones.
Recording speed
Current DVRs record up to 400 pictures per second. The max. record-
ing speed stated is the sum of speeds of the individual camera inputs.
The amount of pictures depends on the resolution. Thus, with such fast
units, a real time recording of max. 25 pictures per second and per
camera is possible.
Duplex method
The unit continues to record, whilst live pictures or previous record-
ings
are viewed. Additionally, with many units, the data can be
accessed
via LAN at the same time.
Alarm recordings
They are possible without delay, as no videotape has to be threaded
in. As a result, the alarm functions like motion detection and external
contacts can be used more intensively and the recorded data quantity
can thus be reduced.
Motion detection
The DVR analyses the video picture. If a change in contrast is noticed,
an alarm is triggered. Various functions can be started with this alarm.
For instance, an automatic recording can be started. Additional
features are possible, like alarm output or sending message via
e-mail, depending on the type of DVR.
LAN
This is the facility to access the DVR via network connection and is often
integrated already. Pictures in one network can be displayed on dif-
ferent computers without extensive extra cabling. An access via the
Internet is also possible by connecting it to a router.
Programmability
a DVR offers many features, which can be adjusted in a clearly
arranged on-screen menu. The different functions like alarm, motion
detection, or video loss work perfectly together. In case of external so-
lutions, many additional cables have to be laid. This makes subsequent
alterations very expensive and causes great effort.