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Pelco Manual C501M-B (10/97) 4-11
4.3.3.4.1 Cable Selection
Coaxitron requires a high quality solid copper core co-
axial cable with at least 95-percent copper braid shield.
Copper-clad steel center conductor is not recommended,
nor is aluminum shield. Such construction is generally
recognized as not being adequate for baseband CCTV
systems. This type of cabling is meant for RF MATV/
CATV type systems only.
4.3.3.4.2 Termination
Coaxitron is sensitive to improper termination and care
must be taken to ensure proper installation. When a
video output from a camera or receiver/driver goes di-
rectly to a video input of the CM8500, the video input
must be terminated with 75 ohms. However, if there is
more than one piece of equipment in the video path,
only the last piece of equipment is terminated. Termi-
nating more than one piece of equipment (double ter-
mination) causes loss of signal.
For example, if a video input to the CM8500 is going
to be looped out to the input of another device, place
the jumper on the buffer card in the CM8500 in the
looping position and terminate the input of the device
receiving its signal from the CM8500. In this case the
CM8500 is between the video source and the final piece
of video input equipment.
If there is any equipment, such as a spot monitor, be-
tween the video input of the CM8500 and the video
output from your camera or receiver/driver, make sure
that these devices are set for looping, or high imped-
ance. Terminate the video input to the CM8500. Here,
the CM8500 is the last piece of equipment.
Other
Camera CM8500 Video Equip.
Looping 75-ohm
Input termination
Video
In Out
Video In
Camera Monitor CM8500
Looping 75-ohm
Input termination
In Out
Video In
Video devices placed between the CPU and receiver/
driver must be passively looping and not use an ampli-
fied looping scheme. Some quad devices and VCRs use
this scheme. The amplified devices are not bidirectional
and therefore do not pass the Coaxitron
®
control sig-
nals. Should these devices need to be installed they must
utilize video that has first looped through the matrix
inputs .
See Section 4.3.3.2 for setting the termination jumpers.