Important information
ix
Triax cable systems
WARNING
Only connect a Triax cable from the same LDK camera family to the unit.
Do not allow system earth currents to exceed 1.5A in the outer shield of the Triax
cable or 0.2A in other cable shields.
To avoid excessive earth currents in a Triax system, galvanically separate the power
earth connection of equipment connected to the camera from the camera earth.
It is strictly prohibited to short circuit the inner and outer shields of a Triax cable
used to connect a camera to a base station.
Galvanic separation
Because of the nature of Triax systems, with long distances between camera and
Base Station, the risk of earth currents flowing is greater. These earth currents can
result in damage to the equipment.
For example, a monitor connected directly to the CVBS output of the camera is
powered locally. The earthing point of the monitor’s power supply can be at a
different potential with respect to the earthing point of the Base Station. If the
power earth of the monitor is also the video earth, then this earth potential is
transferred to the camera via the shield of the BNC connector. The difference in
earth potential between the camera and the Base Station results in an earth current
in the Triax system.
To prevent earth currents from flowing in the Triax system, we recommend galvanic
separation of earthed equipment connected to the camera. This separation can be
achieved by using an isolation transformer between the local power outlet and the
equipment connected to the camera. Alternatively, use equipment that has a
double insulation and therefore does not require an earth connection.
