Network Cable - Belden 8205
CAB/...
Main Features Belden 8205 Cable, unscreened twisted pair Approved cable for the SeaChange Network Also Preferred for all sensors and inputs Network can be any topology, up to 500m per segment

Description of Features

Network Cabling

All SeaChange modules are connected together on a common communications network so that they can exchange information and talk to a PC based Graphical User Interface such as Doorway. The recommended cable for networks is Belden 8205.

The maximum cable length is 500m. This is the total length of cable in a segment regardless of wiring topology. The network can be wired in any form, star, spur, ring or daisy chain but it is the total cable length which needs to be taken into account. The network is polarity independent and it makes no difference if individual modules are connected in the same sense or not, except in the case of power supplies which are polarity sensitive.

If the system to be installed exceeds the 500m limit then the network must be divided up into a number of segments using Repeater Modules. These provide electrical isolation between network segments although communications messages travel seamlessly from one segment to another.

The network cable used must be unscreened twisted pair data cable; ordinary multicore cable is not suitable (even if the conductors appear to be twisted). Conductor size is important; cable with conductors that are too small in cross-section will cause excessive volt-drop, thus reducing the length of the network. Conversely, larger conductor sizes will have increased capacitance, which will also reduce the network length. Belden 8205 cable types optimises both these factors.

Under no circumstances should cable that is not twisted, or two single cables be used for the communications network.

For installations where discreet surface mounted cabling is desired, use an alternative cable Belden 7701with a reduced maximum network length of 350m. This alternative can be installed in a similar way to telephone cable.

Segregation from mains wiring

The network is very resilient to induced common mode noise and the communications cable does not need to be segregated from the mains wiring, however the prudent installer will take simple common sense actions to minimise the amount of induced noise. For example long runs in the same trunking as cables carrying large currents should be avoided where possible. Induced noise into the communications cable decreases markedly with even small (5cm) separations so cable tie the communications cable to the edge of the tray rather than to the mains bearing cables. Cross high current carrying cables at right angles where possible. Within the panel, SeaChange product has the low voltage and communications connections on the lower edge of the modules, and the power and switched circuits on the top edge, so maintaining separation of these different cable types where it is possible at no significant cost is good engineering practice.

Maximum Number of Modules

The Maximum Number of Modules per network segment is limited to 64. The network should be divided with repeaters if there are more than 64 modules. Note that power supplies and Repeaters count as modules with respect to this network loading.

Sensor Cabling

Sensor cabling should be to the same specification as the network - Unscreened, Twisted pair. Recommended maximum cable length 100m. If already installed, screened cables can sometimes be re-used for sensors without detriment provided the screen is continuous and properly earthed at one point only. New installations should always use the correct Unscreened, Twisted pair cable.

Sensors should be of the insulated type and not earthed.

Specification

For further information on cable use, please see our Design Guide publication.

If your usual supplier cannot source the above specified Belden cables, you can purchase the cable direct from SC Controls.

Options and Product Codes

Network Cable

CAB / [option]

Options

SC Controls Ltd

PO Box313
Wadhurst
East Sussex
TN5 6JL

phone 08707 606040
fax 08707 606041
e-mail seachange@sccontrols.co.uk
http:// www.seachange.co.uk