Specifications

KNOW-HOW: Connection of the Cameras
S66
KNOW-HOW · KNOW-HOW · KNOW-HOW · KNOW-HOW · KNOW-HOW · KNOW-HOW · KNOW-HOW
Wireless transmission
In some cases, it is impossible to lay cables, e.g. when crossing a
square or a street. For this purpose, wireless transmission with a
transmitting frequency in the range of 2.4GHz or 5.8GHz can be
used. In the 2.4GHz range a total of 3 from a possible 5 channels
and in the 5.8GHz range 6 from a possible 16 channels are avail-
able at the same time.
When selecting the frequency band, attention must be paid to the
fact that nowadays the W-LAN connections are also established in the
2.4GHz range and a mutual interference can thus not be ruled out.
This frequency overlap does not occur in the 5.8GHz range.
“What kind of operating ranges can be achieved?“ is one of the most
frequently asked question concerning video signal transmission paths.
Predictions on the operating range are difficult to make. The fre-
quency of 2.4 or 5.8GHz does not pass through metal obstacles.
Metal surfaces or metal gates reflect the radiation, i.e. it is diverted
into another direction. The signals can in fact pass through other
obstacles like e.g. walls, windows or bushes and trees, but it partly
results in a considerable attenuation of the signal. In order to achieve
a perfect result, it should, if possible, be ensured that there is no
obstacle between transmitter and receiver (visual contact).
With high-quality systems it is thus possible to achieve distances of
250m. In cases where external reception antennas are used, even
greater distances can be achieved.
The attenuation at walls etc. is also the reason why the distances to be
achieved indoors are less than the great operating ranges achievable
outdoors.
To allow a high flexibility with a wireless transmission, different ver-
sions of the system are available.
Video modulator
For surveillance systems in the private sector, customers frequently
request to transmit the camera picture directly to an existing TV set.
The output of a camera or a digital recorder can generally be con-
nected directly to a SCART or video connection available at current
TV sets. In case several cameras are to be connected or signals are to
be transmitted to different TV sets, the application of video modula-
tors may be useful.
Up to 3 modulators can be combined and
inserted into the antenna system.
The most elegant method is the insertion
directly at the antenna tip or behind the BK
input. The signal of the modulator can then
be received throughout the system and can
be shown on several TV sets.
VB-400V
Camera 1
Quad processor
ENTERENTER
MENUMENU
QUADQUAD AUTAUTOO
VCR PLAVCR PLAYY
EXITEXIT
FREEZEFREEZE
COLOUR QUAD PROCESSOR
TVSP-46COL
+
1
– +
2
– +
3
– +
4
–
+
1
– +
2
– +
3
– +
4
–
VB-400V
Monitor
Camera 2
Camera 3 Camera 4
®
POWER
H-HOLD V-HOLD BRIGHT CONTRAST
18
1 = channel 1, signal +
2 = channel 1, signal –
3 = channel 2, signal +
4 = channel 3, signal –
5 = channel 3, signal +
6 = channel 2, signal –
7 = channel 4, signal +
8 = channel 4, signal –
RJ45
Hum Interference in Video Surveillance Systems
In video surveillance systems where the camera and monitor are lo-
cated in different buildings or sections of a building, e.g. camera in
manufacturing building and monitor in administration building, it hap-
pens time and again that the monitor displays a picture with wavelike
motions.
The picture is generally allright if the camera is connected directly to
the monitor with a short cable.
The applied material is not responsible for this faulty picture, but it
usually turns out that the sections of the building are supplied with a
separate connection for the mains voltage. This is often the case if new
buildings are constructed in addition to existing ones.
An insufficient potential equalization between the old and new mains
results in a potential difference and thus in equalizing currents via the
ground connection of the camera to the monitor and conseqently
causes the interference in the video picture.
In principle, the cause has to be rectified by an expert because other
faults could also be the cause, e.g. data losses on network leads, acti-
vation of protective circuits, or development of excessive contact volt-
age due to the potential difference.
If this is not possible, the application of an isolation transformer of
the type TVI-100 or TVI-300 can mostly rectify the image interference.
In this case, a transformer is connected directly to the video lead.
TVI-100
see page S 70
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®
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