The purpose of this document is to explain how to apply the LongReach 16 Active CCTV
Receiver Hub under different operating conditions and to discuss issues that are not necessarily
covered in the product Datasheet, Installation Guide or CCTV Balun Application Guide.
Function
The function of the LongReach 16 Active CCTV Receiver Hub is to provide a “plug-and
forget” Cat 5 cabling solution for in the CCTV environment. Applications include:
The LongReach 16 has auto-gain control (AGC) that automatically optimizes the video output
signal according to the cable length and other factors that affect signal transmission such as
temperature and cable grade. The AGC optimizes the brightness and sharpness levels of the
video signal so that the image is as good as if the adjustments were performed manually. As
cable length increase, AGC compensation increases as illustrated below.
AGC
Brightness
Sharpness
Cable length
Due to the real time processing of the signal, there is brief time delay before the image is
stabilizes. This may take a two to five seconds. Once the image has stabilized it remains locked
to that setting even if the camera is disconnected from the CCTV hub as shown in the following
diagram.
AGC
Optimum Brightness
Optimum Sharpness
Time
However, if the hub is powered off and on, or a hub port is connected to a different camera,
then the AGC will readjust again. AGC re-adjusts when the signal input levels and/or cable
length changes.
In an existing installation, it may be necessary to add or change cameras on a LongReach 16
Hub. In order to ensure proper functioning of the hub after the new cameras are connected, it is
necessary to first “reset” the hub before bringing the new cameras on-line. This may be
achiev ed by performing one of the following procedures:
Procedure A:
1. Connect the new cameras to the hub while the hub is powered on.
2. Power off the hub for one minute in order to allow the hub to reset.
3. Power on the hub and allow one (1) minute for the auto-gain to stabilize.
Procedure B:
1. Power off the hub.
2. Connect the new cameras to the hub while the hub is powered off.
3. Power on the hub and allow one (1) minute for the auto-gain to stabilize.
Please note that if the above procedure is not followed, then the hub may not properly perform
auto-gain compensation resulting in poor image quality.
Switching Camera Connections
Each port on the LongReach 16 is independently controlled and optimized for the camera and
cable that is connected to it. When a LongReach port is switched to a different camera, either
manually or via a video cross-point switch, the AGC control for that port will automatically
recalculate the optimum settings. This may take up to two or three seconds. The greater the
difference in cable length or signal level between the first camera and the second camera, the
greater will be AGC time delay. When the cable length and signal input level of the switched
ports are similar, the time delay for the image to stabilize will be minimal. Therefore the time
necessary for AGC compensation to stabilize is related to the change in cable length and/or
input signal levels.
The LongReach 16 may be deployed in various cabling topologies depending on the type of
CCTV system and the architectural layout of the site. There are three basic layouts shown in
the following diagrams.
Camera to Head End – Short Distance
In this scenario, the LongReach 16, central monitoring equipment and remote power are all colocated.
In regard to the cabling, siamese cables for video, power and control may be installed between
the central monitoring room. Alternatively, Cat5 cables may be used to transport video, power
and control to the camera. It is important to note that if remote power is transmitted via Cat5
cable, a Class II power supply must be used.
Camera to Head End – Extended Distance
In this layout the LongReach 16 and the central monitoring equipment are co-located and due
the distance, remote power to the camera is supplied locally.
In some installations, it is more practical to install the cabling hardware in a remote telecom
room and insert remote power and control if necessary at this point. Here too, siamese cables
may be used between the telecom room and the cameras. Alternatively, Category 5 cables
may be used to carry all three signals. A Cat5 “110” style patch panel may be used to
concentrate all three signals over one Cat5 cable. It is important to note that if remote power is
transmitted via Cat5 cable, a Class II power supply must be used.