3.3 Wiring Implementation

Twisted-Pair Construction

CrossOver Cables vs Straight Through Cables

Straight through cables have wires that much up with the same pins on the opposite connector. Crossover Cables are used to connect computers together w/o use of switches for communication. Connectors on these cables have to connect between their transmit to the opposite ends' receive.

ie. pair the TIA568A with TIA568B to make a crossover cable.

Straight-Through Cables

• Most twisted pair cables are manufactured as straight-through cables
• Connect computers to a hub or switch with a straight-through cable.
• The pinout order on a computer's network interface card (NIC) is different than the pinout order on the hub or switch port.
• Transmit pins of the NIC map to the receive pins on hub or switch and vice versa.

If a network device such as a hub or switch does not have an uplink port, use a crossover cable when connecting it to another network device.

You can also connect one computer directly to another using a crossover cable. A crossover cable maps the transmit pins on one end of the cable with the receive pins on the other end.

You can easily create a crossover cables as follows:

• Use the T568A standard to attach an RJ45 connector to one end.
• Use the T568B standard to attach an RJ45 to the other end.

RJ45 Wiring Conventions

Pin	TIA568A Order	TIA568B Order
1	Green w/ White	Orange w/ White
2	Green	Orange
3	Orange w/ White	Green w/ White
4	Blue	Blue
5	Blue w/ White	Blue w/ White
6	Orange	Green
7	Brown	Brown w/ White
8	Brown w/ White	Brown

Gigabit Ethernet Cabling

10-Mbps (10BASE-T) and 100-Mbps (100BASE-TX)

You use only 2 pairs of wires in Cat 3, Cat 5, or Cat 5e.

Computer NIC:

• Pin 1: Transmit +
• Pin 2: Transmit -
• Pin 3: Receive +
• Pin 6: Receive -

Pins 4, 5, 7, and 8 are unused.

1000BASE-T or Gigabit Ethernet

Uses all four pairs of wires in Cat 5e and above.

• There are positive (+) and negative (-) pins for each pair of wires.
• Signals go in both directions over each pair of wires, so there are no dedicated transmit and receive pins.
• The T568A and T568B wiring standards are still used.

If Cat 7 cabling is used for 10 Gigabit Ethernet, the cables are terminated with GG45 or TERA connectors.

• GG45 connectors require a special set of tools that are different from the RJ45 crimping tool.
• TERA connectors can be installed without any special tools.

Power over Ethernet Cabling (POE)

Lets you carry power over ethernet like a phone being powered.

• power is through unused pairs of wires in 10/100-Megabit Ethernet
• Power can be done via data wires
• Many network switches can apply PoE
• PoE injection devices can be added to the middle of the cable span

Wiring Distribution

Demarc

The demarcation point is where the line enters the building. Responsibility is determined on which side the point this occurs. ie. inside the building is for the network admin, outside is the ISP.

This is also known as the mininum point of entry (MPOE) or end user point of termination (EU-POT). Sometimes, we may need a Demarc extension in order to extend the line to the IDF where its actually needed.

Distribution Frames (MDF and IDF) and Building Industry Cross-Connect (BIX)

The MDF is the main wiring closet, from there it gets connected to IDFs using vertical cross connects, typically located above the MDF.

MDF: A traditional MDF may exist in a dedicated room or a within rack space in a datacenter. An MDF is usually located on the bottom floor or basement of a building. All internet or WAN demarcation points are normally near or within the MDF.

IDFs: IDFs are typically located on each floor directly above the MDF, although additional IDFs can be added on each floor as necessary. IDFs located above the MDF are connected using a vertical cross connect (VCC) or wire bundles that run vertically between the MDF and an IDF. If a floor has more than one IDF, the IDFs are connected with a horizontal cross connect (HCC).

BIX is certified for Cat 5e composed primarily of 2 parts

Punchdown Blocks

66 block

• 66 block has 25 rows of 4 metal pins, pushing wire into pin pierces plastic sheath
• Connects individual copper wires together
• in the 25-pair block (non-split block) all pins are bonded/electrically connected. this connects a single wire with up to 3 other wires
• 50-pair block (split block), each set of two pins in a row are bonded. we use this to connect a single wire to another. bridge clips connect pins and are used in troubleshooting/testing

When using with data:

• be sure to use blocks rated for cat 5
• when inserting wires, place both wires in a pair through the same slot to preserve the twist

110 Block

• 110 block comes in different sizes (50, 100, 300 pair)
• Has rows of plastic slots, with each slot connecting two wires Place the first wire into the plastic slot on the 110 block. Insert a connecting block over the wire and slot. The connecting block has metal connectors that pierce the plastic cable sheath. Place the second wire into the slot on the connecting block.
• C4 connectors connect 4 pairs of wires; C5 connectors connect 5 pairs
• Connecting Wires should be done in a specific order: White wire with a blue stripe followed by the solid blue wire. White wire with an orange stripe followed by the solid orange wire. White wire with a green stripe followed by the solid green wire. White wire with a brown stripe followed by the solid brown wire.
• 110 is mostly used for telephone applications. Preferred over 66-block, because they introduce less crosstalk

When using with data:

• Use blocks rated for Cat 5, 6, and 6a
• Inserting wires, preserve the twist

Krone is an alternative to the 110 block.

Block Type	Description
66 block	A 66 block is a punch down block used to connect individual copper wires together.

• The 66 block has 25 rows of four metal pins. Pushing a wire into a pin pierces the plastic sheath on the wire, making contact with the metal pin.
• There are two different 66 block configurations:
  • In the 25-pair block (also called a non-split block), all four pins are bonded (electrically connected). Use the 25-pair block to connect a single wire with up to three other wires.
  • With the 50-pair block (also called a split block), each set of two pins in a row are bonded. Use the 50-pair block to connect a single wire to one other wire.
• With a 50-pair block, use a bridge clip to connect the left two pins to the right two pins. Adding or removing the bridge clip is an easy way to connect wires within the row for easy testing purposes.

66 blocks are used primarily for telephone applications. When used for data applications:

• Be sure to purchase 66 blocks rated for Cat 5.

• When inserting wires in the block, place both wires in a pair through the same slot to preserve the twist as much as possible. | | 110 block | A 110 block is a punch down block used to connect individual wires together.

• The 110 block comes in various sizes for connecting pairs of wires (for example 50, 100, or 300 pair).

• The 110 block has rows of plastic slots. Each plastic slot connects two wires together.

  • Place the first wire into the plastic slot on the 110 block.
  • Insert a connecting block over the wire and slot. The connecting block has metal connectors that pierce the plastic cable sheath.
  • Place the second wire into the slot on the connecting block.

• C4 connectors connect four pairs of wires; C5 connectors connect five pairs of wires.

• When connecting data wires on a 110 block, you typically connect wires in the following order:

  • White wire with a blue stripe followed by the solid blue wire.
  • White wire with an orange stripe followed by the solid orange wire.
  • White wire with a green stripe followed by the solid green wire.
  • White wire with a brown stripe followed by the solid brown wire.

110 blocks are used primarily for telephone applications. They are preferable over 66 blocks in high-speed networks because the introduce less crosstalk. When used for data applications:

• Be sure to purchase 110 blocks that are certified for Cat 5, Cat 6 and Cat 6a.
• When inserting wires, preserve the twist as much as possible. | | Krone LSA-PLUS | Krone is an insulation-displacement connector for telecommunications. It's a European alternative to the 110 block. The Krone system is also used in broadcast systems with audio interconnections. The krone wiring can be used with associated control systems as well. Multipair audio cables are specifically designed for the krone system. |