Cabinet Layout and Design

The detailed layout of communications racks varies naturally from installation to installation but  there is an overall scheme that has become standardised. The scheme allows for the expansion of the wiring network and maintains a consistent arrangement of equipment without the need for constant reorganisation when additions are made.

The rack must accommodate six main classes of equipment:

1.  Permanent UTP cabling to users' outlets. This is presented in the form of RJ45 patch fields.

2.  Permanent twisted pair connections to incoming voice circuits from the Building Distribution Frame (BDF). These too are presented in the form of RJ45 patch fields.

3.  Active communications equipment connected to the campus data network. These always require an electrical mains supply but they vary widely. They are commonly ether switches presenting their output ports on RJ45 sockets.

4.  Optical fibre terminations that provide the actual link to the campus data network. These are usually presented in the form of a 'fibre tray' with the connexions protected by dust caps. Occasionally, the connexion to the campus data network may be achieved by means other than optical fibres. (e.g. UTP cables).

5.  Cable management components. These usually take the form of metal loops to retain the cables used to make the patched connections between active equipment and users' sockets. NOTE: The use of nylon cable ties is now not permitted. Cable bundles are to be formed/secured using reusable fabric hook and loop ties ('Velcro'). This form of cable tie allows additions and changes to be made easily, does not distort cables and does not tear the skin.

6.  Electrical mains distribution. These components are installed as a bank of unswitched 15A mains sockets.

The total available rack space is divided into the following classes:

1.  Patching for users' sockets is located at the front-top of the rack and expands downwards towards the bottom of the rack.

2.  Patching for voice circuits is located at the front-near-bottom of the rack and expands upwards towards the top of the rack.

3.  Active communications equipment is located in the front-middle of the rack and expands either towards the voice patching fields or towards the users' outlet patching fields as space permits.

4.  Optical fibre trays are located below the voice-patching field at the front-near-bottom of the rack and expand downwards.

5.  Cable management bars for patch cables are located at the front-topmost position of the rack and then at every fourth position thereafter. Cable management for permanent wiring is located at the back of the cabinet and secured using fabric hook and loop ties ('Velcro').

6.  Mains distribution for the rack is located at the back of the cabinet and is fed from an unswitched fused spur which is in turn derived from an independent way on the mains distribution board within the building. The mains cables to the comms equipment should form into a neat cable loom with fabric hook and loop ties and kept away from any voice or data cables. In addition, the mains cables should be marked with identical labels at both the

15A-plug end and at the IEC socket end in order to identify the cable without disturbing the cable loom.

7.  The metalwork of the rack or cabinet should be bonded to earth.