Specifications

Security 2009
KNOW-HOW: Connection of the Cameras
S64
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The right selection of connection cables for the video signal and the power supply is part of
effectively planning an analog video surveillance system.
Different methods can be considered for the video signal:
• Video signal via coaxial cable
• Special version: one-cable technique
• Transmission via 2-wire cable
• Modulation and transmission via RF transmitter
• Modulation and insertion into antenna systems
Transmission via coaxial cable
The coaxial cable is the method most commonly used for connect-
ing video components. In this case, the video signal is transmitted
directly.
A special video cable is used as the cable, e.g. VCC-59 with an
impedance of 75 Ω.
In addition to BNC cables where the connectors are already fitted,
cables which are sold by the metre are also often used. The right con-
nectors are then fitted on-site.
How long may a connection cable be?
This may be the most frequently asked question. The max. length of the cable depends on the
attenuation of the applied type of cable. The general rule states: the greater the cable thick-
ness, the lower the attenuation and the longer the applied cable may be.
The max. attenuation of the connection cable should not exceed 3 dB, because a reduc-
tion of a signal by 3 dB results in a reduction of the level by 50 %.
Current digital recorders in particular show picture interference if the level is too low.
The cable RG-59 is the most frequently used cable which provides an attenuation of 2.4 dB
per 100 m at 5 MHz.
With an allowed 3dB attenuation, the cable length for the VCC-59 is 125 m max.
The signal does not disappear straightaway with a cable length of 126 m, but with increas-
ing cable length the fine details and sharp outlines will be reduced, because the high fre-
quencies which produce these signals will be attenuated the most.
Signal distribution
It is often required to distribute one video signal to several video
inputs. This distribution should always be carried out by an active
video splitter.
A further possibility is to transmit the video signal from one unit to
another. For this purpose, many units feature feed-through outputs
which are also called LOOP outputs. This output transmits the signal
with the right level to the successive unit.
The application of a basic BNC T-piece should be avoided. This results in a reduction of
the available level by 50% and most propably in picture interference during further pro-
cessing.
Connection of the Cameras