1. CIS 1140 Network Fundamentals
Chapter 3 Transmission Basics and Networking Media
Collected and Compiled
By JD Willard
MCSE, MCSA, Network+,
Microsoft IT Academy Administrator
Computer Information Systems Instructor
Albany Technical College

2. Attention: Accessing Demos
This course presents many demos.
The Demos require that you be logged in to the Virtual Technical College web site when you click on them to run.
To access and log in to the Virtual Technical College web site:
To access the site type in the url window
Log in using the username: CIS 1140 or ATCStudent1
Enter the password: student (case sensitive)
If you should click on the demo link and you get an Access Denied it is because you have not logged in to vtc.com or you need to log out and log back in.
If you should click on the demo link and you are taken to the VTC.com web site page you should do a search in the search box for the CompTIA Network+ (2009 Objectives) Course and run the video from within that page.

3. Objectives
Explain basic data transmission concepts, including full duplexing, attenuation, and noise
Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media
Compare the benefits and limitations of different networking media
Explain the principles behind and uses for serial connector cables
Identify wiring standards and the best practices for cabling buildings and work areas

4. Transmission Basics
In data networking, transmit means to issue signals to the network medium
Transmission refers to either the process of transmitting or the progress of signals after they have been transmitted
Transceiver
Transmits and receives signals
Cabling Basics Demo
Cabling Demo

5. Analog and Digital Signals
Information transmitted via analog or digital signals
Signal strength proportional to voltage
In analog signals, voltage varies continuously and appears as a wavy line when graphed over time
Wave’s amplitude (the height of the wave) is a measure of its strength at given point in time
Frequency: number of times wave’s amplitude cycles from starting point, through highest amplitude and lowest amplitude, back to starting point over a fixed period of time
Measured in Hz
Wavelength: distance between corresponding points on a wave’s cycle
Phase: progress of a wave over time in relationship to a fixed point
Analog transmission susceptible to transmission flaws such as noise

6. Analog signal benefit over digital More variable
An example of an analog signal
Analog signal benefit over digital
More variable
Convey greater subtleties with less energy
Drawback of analog signals
Varied and imprecise voltage
Susceptible to transmission flaws

7. Analog and Digital Signals
Digital signals composed of pulses of precise, positive voltages and zero voltages
Positive voltage represents 1
Zero voltage represents 0
Binary system: uses 1s and 0s to represent information
Easy to convert between binary and decimal
Bit: a single binary signal
Byte: 8 bits
Typically represents one piece of information
Overhead: describes non-data information that must accompany data for a signal to be properly routed and interpreted

8. Transmission Direction: Simplex, Half-Duplex, and Duplex
Simplex transmission: signals may travel in only one direction (TV or Radio)
Half-duplex transmission: signals may travel in both directions over a medium
Only one direction at a time (Walkie Talkies or Intercom System)
Full-duplex or duplex: signals free to travel in both directions over a medium simultaneously (Telephone)
Used on data networks
Channel: distinct communication path between nodes
May be separated logically or physically
Full Duplex vs Half Duplex Demo

9. Transmission Direction: Multiplexing
Multiplexing: transmission form allowing multiple signals to travel simultaneously over one medium
Channel logically separated into subchannels
Multiplexer (mux): combines multiple signals
Sending end of channel
Demultiplexer (demux): separates combined signals and regenerates them in original form
Receiving end of channel

10. Relationships Between Nodes
Point-to-point transmission involves only one transmitter and one receiver.
Point-to-multipoint transmission involves one transmitter and multiple receivers.
Broadcasts involve one transmitter and multiple, undefined receivers
Nonbroadcast point-to-multipoint transmission issues signals to multiple, defined recipients

11. Throughput and Bandwidth
Throughput: measure of amount of data transmitted during given time period
Measured in bits per second, kilobits per second, megabits per second etc.
Probably most significant factor in choosing transmission method
Limited by signaling and multiplexing techniques used in given transmission method
Transmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connections
Noise and devices connected to transmission medium can limit throughput
Bandwidth: difference between highest and lowest frequencies that a medium can transmit
Range of frequencies
Measured in Hertz or cycles
1 Hertz is the measure of a signal from its starting point to it’s highest amplitude to it’s lowest amplitude and back to the starting point

12. Baseband and Broadband
Baseband: digital signals sent through direct current (DC) pulses applied to a wire
Requires exclusive use of wire’s capacity
Baseband systems can transmit one signal at a time
Half-duplex or duplex transmission
Example: Ethernet
Broadband: signals modulated as radiofrequency (RF) analog waves that use different frequency ranges
Does not encode information as digital pulses
Simplex transmission
Communication Methods Demo

13. Transmission Flaws: Noise
Electromagnetic interference (EMI): waves emanating from electrical devices or cables
Radio frequency interference (RFI): electromagnetic interference caused by radiowaves
Crosstalk: signal traveling on a wire or cable infringes on signal traveling over adjacent wire or cable
Certain amount of signal noise is unavoidable
All forms of noise measured in decibels (dB)

14. Attenuation An analog signal distorted by noise and then amplified
Attenuation can be described as the loss of signal strength as the signal flows away from it’s source. It is caused by resistance on electrical networks and by optical loss on fiber optic networks.
An analog signal distorted by noise and then amplified
A digital signal distorted by noise and then repeated

15. Latency Delay between transmission and receipt of a signal
May cause network transmission errors
Many possible causes:
Cable length
Intervening connectivity device (e.g., modems and routers)
Round trip time (RTT): Time for packets to go from sender to receiver and back
Cabling rated for maximum number of connected network segments
Transmission methods assigned maximum segment lengths

16. Network Cables
A cable is the medium that provides the physical foundation for data transmission
Several types of cable are commonly used
Some networks use only one type of cable, while others employ several cable types
The type of cable chosen depends on:
The size of the network
The protocols being used
The network’s physical layout, or topology
Network Transmission Media Demo
New and Old Cables and Connectors Demo

17. Common Media Characteristics: Throughput
Probably most significant factor in choosing transmission method
Match networking needs with media characteristics
Limited by signaling and multiplexing techniques used in given transmission method
Transmission methods using fiber-optic cables achieve faster throughput than those using copper or wireless connections
Laws of Physics, noise, and devices connected to transmission medium can limit throughput

18. Cost Precise costs difficult to pinpoint Media cost dependencies
Existing hardware, network size, labor costs
Variables influencing final cost of implementing specific type of media
Installation cost
New infrastructure cost versus reuse
Maintenance and support costs
Cost of lower transmission rate affecting productivity
Cost of downtime
Cost of obsolescence

19. Noise Immunity Noise distorts data signals
Distortion rate dependent upon transmission media
Fiber-optic: least susceptible to noise
Limit noise impact on network
Cable installation
Far away from powerful electromagnetic forces
Select media protecting signal from noise
Antinoise algorithms

20. Size and Scalability
Three specifications determine size and scalability of networking media:
Maximum nodes per segment
Depends on attenuation and latency
Maximum segment length
Depends on attenuation, latency, and segment type
After certain distance, signal loses strength
Cannot be accurately interpreted
Populated segment contains end nodes
Unpopulated: no end nodes
Also called link segment
Maximum network length
Sum of network’s segment lengths
Media Distance and Speed Limitations (5:48)

21. Connectors and Media Converters
Connectors are the pieces of hardware that connect the wire to the network device.
Every medium requires a specific kind of connector
Affect costs
Installing and maintaining network
Ease of adding new segments or nodes
Technical expertise required to maintain network
Media converter: hardware enabling networks or segments running on different media to interconnect and exchange signals
Type of transceiver
Device that transmits and receives signals
Copper wire-to-fiber media converter
Converting Media (5:10)

22. Coaxial Cable
Coaxial cable is an older technology that is usually implemented with a bus topology. It is not suitable for ring or star topologies because the ends of the cable must be terminated. It is composed of two conductors, which share a common axis, within a single cable.
Advantages
Disadvantages
Highly resistant to EMI (electromagnetic interference)
Highly resistant to physical damage
Expensive
Inflexible construction (difficult to install)
Unsupported by newer networking standards
UTP, STP, and Coaxial Cabling (5:53)

23. Coaxial Cable Coaxial cable is built with the following components:
Two concentric metallic conductors:
The inner conductor, which carries data signals. It is made of copper or copper coated with tin.
The mesh conductor is a second physical channel that also grounds the cable. It is made of aluminum or copper coated tin.
The insulator, which surrounds the inner conductor, keeps the signal separated from the mesh conductor. It is made of PVC plastic.
The mesh conductor, which surrounds the insulator and grounds the cable. It is made of aluminum or copper coated tin.
The PVC sheath, which is the cable encasement. It surrounds and protects the wire. It is made of PVC plastic.
Coaxial Cable Demo

24. Coaxial Cable Types
The table below describes the different coaxial cable grades.
Grade
Uses
Resistance Rating
RG-58
10Base2 Ethernet networking (also called Thinnet)
50 ohms
RG-59
Cable TV and cable networking
75 ohms
RG-6
Cable TV, satellite TV, and cable networking RG-6 has less signal loss than RG-59, and is a better choice for networking applications, especially where longer distances (over a few feet) are involved.
RG-8
10Base5 Ethernet networking (also called Thicknet)
When using coaxial cables, it is important to use cables with the same resistance (impedance) rating.

25. Coaxial Connectors
Connectors: pieces of hardware connecting wire to network device
Every networking medium requires specific kind of connector
Connector
Description
Twisted onto the cable
Used to create cable and satellite TV connections
Used to connect a cable modem to a broadband cable connection
                                           
Molded onto the cable
Used in 10Base2 Ethernet networks
F-type connector
BNC
Connectors Demo

26. Coaxial Connectors Connector Description
A DB15 serial connector serves as the attachment unit interface (AUI) on the NIC and on the transceiver
Requires a drop cable from the NIC to the transceiver
Connected to the transceiver is a Vampire Tap with a screw or “tooth” that pierces the cable to connect to the conducting core of a thick coaxial cable
Used in 10Base5 Ethernet networks
AUI
10BASE5 vampire tap & transceiver

27. Coaxial Cable Networks
Thin Ethernet, Thinnet, or Black Ethernet: more flexible and easier to handle and install than Thicknet
10BASE-2 Ethernet
Requires RG-58 A/U coaxial cable, BNC-T connectors
Each end of the cable segment must be terminated with a 50 ohm resistor
Conforms to the Rule of network which states that a network can contain up to 5 cable segments, connected by 4 repeating devices, but only three of the cable segments can contain end nodes.

28. Coaxial Cable Networks
Thickwire Ethernet, Thicknet, Yellow Ethernet: original Ethernet medium
10BASE-5 Ethernet Standard
Requires RG-8 coaxial cable, AUI connectors, Transceiver/Vampire Tap, and Drop cable.
Each end of the cable segment must be terminated with a 50 ohm resistor
Conforms to the Rule of network which states that a network can contain up to 5 cable segments, connected by 4 repeating devices, but only three of the cable segments can contain end nodes.

29. Twisted-Pair Cable
Twisted pair cables support a wide variety of fast, modern network standards. Twisted pair cabling is composed of the following components:
Two wires that carry the data signals (one conductor carries a positive signal; one carries a negative signal). They are made of 22 or 24 gauge copper wiring.
PVC or plenum plastic insulation surrounds each wire. Plenum cable is fire resistant and non-toxic. It must be used when wiring above ceiling tiles. PVC cable cannot be used to wire above ceilings because it is toxic when burned.
Two wires are twisted to reduce the effects of electromagnetic interference (EMI) and crosstalk. Because the wires are twisted, EMI should affect both wires equally and can be cancelled out.
The number of twists per meter or foot determines how resistant the pair will be to noise but increases attenuation
TIA/EIA 568 standard divides twisted-pair wiring into several categories
Level 1 or CAT 3, 4, 5, 5e, 6, 6e, 7
Cable Categories (3:34)

30. Twisted-Pair Cable Advantages:
Is relatively inexpensive, easy to install, and capable of spanning significant distances before additional equipment is required
Can accommodate several different topologies, but is most often used in a star topology
Can handle the faster networking transmission rates in use today
Multiple wire pairs are bundled together in an outer sheath. Twisted pair cable can be classified according to the makeup of the outer sheath:
Shielded Twisted Pair (STP) has a grounded outer copper shield around the bundle of twisted pairs or around each pair. This provides added protection against EMI.
Unshielded Twisted Pair (UTP) does not have a grounded outer copper shield. UTP cables are easier to work with and are less expensive than shielded cables.
UTP Cable Demo
Twisted Pair Cabling and Connectors Demo

31. Shielded Twisted-Pair (STP)
The cable consists of insulated wire pairs that are surrounded by a metal shielding, such as foil
The effectiveness of the shield depends on the environmental noise to which STP is subjected, the grounding mechanism, and the material, thickness, symmetry and consistency of the shielding
Barrier to external electromagnetic forces
Contains electrical energy of signals inside
STP is more expensive than UTP, but does provide better immunity to EMI and RFI
STP cable
STP Cable Demo

32. UTP (Unshielded Twisted-Pair)
Less expensive, less resistant to noise than STP
The cable contains color-coded pairs of insulated copper wires inside a plastic jacket
Each pair has a different number of twists per inch, depending on the grade, to help eliminate interference from adjacent pairs or cables
Categories:
CAT 3 (Category 3): up to 10 Mbps of data at 16 MHz
CAT 4 (Category 4): 16 Mbps throughput at up to 20 MHz
CAT 5 (Category 5): up to 1000 Mbps throughput at 100 MHz
CAT 5e (Enhanced Category 5): higher twist ratio 350 MHz
CAT 6 (Category 6): six times the throughput of CAT 5. Wires encased in foil. 250 MHz
CAT 6e (Enhanced Category 6): reduced attenuation and crosstalk. Capable of 550 MHz.
CAT 7 (Category 7): signal rates up to 1 GHz. Contains sheilding and uses different connectors.

33. Twisted Pair Connectors
Description
RJ-11
                      
Has 4 connectors
Supports up to 2 pairs of wires
Uses a locking tab to keep connector secure in outlet
Used primarily for telephone wiring
RJ-45
                              
Has 8 connectors
Supports up to 4 pairs of wires
Used for Ethernet and some token ring connections
Copper Connectors (10:29)

34. Comparing STP and UTP Characteristics
Throughput: STP and UTP can both transmit data at 10, 100, and 1000 Mbps
Depending on grade of cabling and transmission method used
Cost: STP usually more expensive than UTP
Connector: Both use RJ-45 for data and RJ-11 for phones
Noise Immunity: STP more noise-resistant
Size and scalability: Max segment length for both is 100 meters
Maximum of 1024 nodes

35. Terminating Twisted Pair Cable
Patch cable
Relatively short cable
Connectors at both ends
Proper cable termination techniques
Basic requirement for two nodes to communicate
Poor terminations:
Lead to loss or noise
TIA/EIA standards
TIA/EIA 568A
TIA/EIA 568B

36. TIA/EIA 568A Series
In the T568A standard the green and green and white striped wire transmits data from the device, while the orange wire and the orange and white striped wire receives data from the network.
TIA/EIA 568A standard terminations

37. TIA/EIA 568B Series
In the T568B standard the orange and orange and white striped wire transmits data from the device, while the green wire and the green and white striped wire receives data from the network.
It typically doesn’t matter which scheme you choose, but to avoid confusion and potential transmission errors you should ensure that you cable all wiring on your LAN according to one standard.
TIA/EIA 568B standard terminations

38. Straight-Through Cable
Description
Straight-through
Computers connect to the network through a hub or switch with a straight- through cable. There are two standards for creating straight-through cables:
T568A--To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: GW, G, OW, B, BW, O, BrW, Br.
T568B--To use this standard, arrange the wires from pins 1 to 8 in each connector in the following order: OW, O, GW, B, BW, G, BrW, Br.
It doesn't matter which standard you use, but once you choose a standard, you should do all your cables that way to avoid confusion during troubleshooting.
Crossover and Straight Through Cables (6:27)

39. Crossover Cable
Crossover cables are used to wire two computer’s network cards together without the use of a hub/switch or to wire two hubs/switches together through their data ports (stacking)
To create a crossover cable wire one end of the cable 568A and the other end 568B

40. Device Connection
When connecting Ethernet devices, it is important that the transmit (Tx) wires from one device are matched with the receive (Rx) wires on the other device. To help understand how to connect devices together, be aware of the following:
Network interface cards in workstations and routers send data on the transmit pins and expect to receive data on the receive pins.
Between any two ports used for connecting devices to a hub or a switch, crossing is automatically performed within the hub or the switch.
Uplink ports on hubs and switches are not crossed.

41. Cable Type - Usage Cable Type Use
Straight-through
A straight-through cable connects each wire to the same pin on each connector (pin 1 to pin 1, pin 2 to pin 2, etc.). Use a straight-through cable when the crossover is performed with a hub or a switch. Use a straight-through cable when connecting the following devices:
Workstation to a regular port on a hub or switch
Router to a regular port on a hub or a switch
Regular port on a hub or switch to an uplink port on a hub or a switch
Crossover
A crossover cable matches the transmit (Tx) wires on one connector with the receive (Rx) wires on the other connector. Use a crossover cable when crossing is not performed automatically, or when crossover is being performed twice. Use a crossover cable when connecting the following devices:
Workstation to a workstation, router to a router, or workstation to a router (in a back-to-back configuration)
Uplink port on a hub or a switch to an uplink port on a hub or a switch
Workstation or a router to the uplink port on a hub or a switch
Hub or switch using a regular port to a hub or a switch using the regular port

42. Straight-through Patch Cable Assembly Instructions
Strip the cable jacket back about 3/4 of an inch from the end of the cable
Sort the pairs so they fit into the connector in the correct order
Insert the pairs into the connector
Crimp the pins with a crimp tool
Repeat for other end and test cable

43. Twisted Pair Wiring Tools
Termination tools
Wire cutter
Wire stripper
Crimping tool
After making cables:
Verify data transmit and receive
Crimpers (3:36)

44. Fiber-Optic Cable
To connect computers using fiber optic cables, you need two fiber strands. One strand transmits signals, and the other strand receives signals. Fiber optic cabling is composed of the following components:
Fiber-optic cable (fiber)
One or more glass or plastic fibers at its center (core) carries the signal
Cladding
The cladding maintains the signal in the center of the core as the cable bends. It is made of a different density of plastic or glass.
Kevlar strands
Give the cable strength and allow it to avoid stretching
A Plastic sheath covers the kevlar strands and protects the cladding and the core
Data transmission
Pulsing light sent from laser or light-emitting diode (LED) through central fibers
A fiber-optic cable

45. Fiber-Optic Cable Advantages Disadvantages
Totally immune to EMI (electromagnetic interference)
Highly resistant to eavesdropping
Supports extremely high data transmission rates
Allows greater cable distances without a repeater
Industry standard for high-speed networking
Very expensive
Difficult to work with
Special training required to attach connectors to cables
Fiber Optic Cable Demo

46. Fiber Optic Characteristics
Throughput
transmission rates exceed 10 Gigabits per second
Cost
most expensive of the transmission mediums
Connector
10 different types of connectors
typically use ST, SC, LC, or MTRJ connectors
Noise immunity
unaffected by EMI, RFI, or crosstalk
Size and scalability
segment lengths vary from 150 to 40,000 meters
Suffers from optical loss
degradation of light signal after it travels a certain distance away from its source

47. Fiber Optic Cables Type Description Single Mode (SMF) Multi-mode (MMF)
Transfers data through the core using a single light ray (the ray is also called a mode)
The core diameter is around 10 microns
Supports a large amount of data
Cable lengths can extend a great distance
Rarely used for shorter connections
Due to cost
Transfers data through the core using multiple light rays
The core diameter is around 50 to 100 microns
Cable lengths are limited in distance
Common uses
Cables connecting router to a switch
Cables connecting server on network backbone
Multimode and Singlemode Fiber (4:46)

48. Fiber Optic Connectors
Figure SC (subscriber connector or standard connector)
Figure 3-33 ST (straight tip) connector
Figure 3-36 MT-RJ (mechanical transfer-register jack) connector
Figure 3-35 LC (local connector)
Fiber Connectors (4:36)

49. Fiber-Optic Converters
Required to connect multimode fiber networks to single-mode fiber networks
Also fiber- and copper-based parts of a network
Single-mode to multimode converter
Courtesy Omnitron Systems Technology

50. Serial Cables Data transmission style
Figure 3-37 DB-9 connector
Figure 3-38 DB-25 connector
Data transmission style
- Pulses issued sequentially, not simultaneously
RS-232 (Recommended Standard 232)
EIA/TIA standard
Physical layer specification
Signal voltage, timing, compatible interface characteristics
Connector types
RJ-45 connectors, DB-9 connectors, DB-25 connectors
RS-232 used between PC and router today
RS-232 connections
Straight-through, crossover, rollover

51. Structured Cabling
Structured cabling specifies standards without regard for the type of media or transmission technology used on the network.
Structured cabling is based on a hierarchical design that divides cabling into subsystems.
You should be familiar with the principles of structured cabling before you attempt to design, install, or troubleshoot an organization’s cable plant.
Cable plant
hardware making up enterprise-wide cabling system

52. Structured Cabling Components Entrance facilities
MDF (main distribution frame)
Cross-connect facilities
IDF (intermediate distribution frame)
Backbone wiring
Telecommunications closet
Horizontal wiring
Work area
TIA/EIA structured cabling in an enterprise
TIA/EIA specifications for backbone cabling

53. Entrance facilities or Demarcation point (demarc)
When you contract with a local exchange carrier (LEC) for data or telephone services, they install a physical cable and a termination jack (Smart Jack) onto your premises. The demarcation point (demarc) is the line that marks the boundary between the telco equipment and the private network or telephone system.
Typically, the LEC is responsible for all equipment on one side of the demarc, and the customer for all equipment on the other side of the demarc.
The demarc is typically located in the bottom floor of a building, just inside the building.
The demarc is often identified by an orange plastic cover on the wiring component.
Demarcs and Smart Jacks (3:39)

54. Main Distribution Frame (MDF)
The main distribution frame (MDF), also known as the main cross-connect or the Equipment room, is the main wiring point for a building.
The MDF is the interconnection point between the LAN/WAN and the service provider’s facility.
The MDF is typically located on the bottom floor or basement. The LEC typically installs the demarc to the MDF.
The location of significant networking hardware, such as servers and mainframe hosts.
IDF and MDF (3:33)

55. Intermediate Distribution Frame (IDF) or Telecommunications Closet An intermediate distribution frame (IDF) is a smaller wiring distribution point within a building. IDFs are typically located on each floor directly above the MDF, although additional IDFs can be added on each floor as necessary. The IDF or telecommunications closet contains connectivity for groups of workstations in an area, plus cross connections to equipment rooms

56. Vertical cross connect
Backbone Wiring
Backbone wiring or Vertical cross-connect: interconnection between telecommunications closets, equipment rooms, and entrance facilities
Vertical cross connect
A vertical cross connect connects the MDF on the main floor to IDFs on upper floors. Cabling runs vertically (up and down) between the MDF and the IDFs.
Horizontal cross connect
A horizontal cross connect connects IDFs on the same floor. Cabling runs horizontally (sideways) between the IDFs.

57. Work Area
The Work Area encompasses all patch cables and horizontal wiring necessary to connect workstations, printers, and other network devices from NICs to telecommunications closet

58. TIA/EIA structured cabling in a building
Horizontal Wiring
Horizontal wiring is the wiring connecting workstations to the closest telecommunications closet

59. Horizontal Wiring Subsystem
Horizontal wiring subsystem —TIA/EIA recognizes three possible cabling types for horizontal wiring: STP, UTP, or fiber-optic. The maximum allowable distance for horizontal wiring subsystem is 100 m. This span includes 90 m to connect a data jack on the wall to the telecommunications closet plus a maximum of 10 m to connect a workstation to the data jack on the wall plus the cross connect.

60. Patch panel
Patch panel
A patch panel is a device that typically connects individual stranded wires into female RJ-45 connectors. For example, you might connect 4 pairs of wires from a punchdown block to a port on the patch panel.
On the patch panel, you then connect drop cables (cables with RJ-45 connectors) to the patch panel on one end and a computer on the other end.

61. Wiring Rack
Punchdown block
Patch Panel

62. “Telco Room”
Only twisted pair can be terminated in the punch down block.

63. Data Outlet

64. Data Outlet

65. Installing Cable
Many network problems can be traced to poor cable installation techniques
Two methods of inserting UTP twisted pairs into RJ-45 plugs: TIA/EIA 568A and TIA/EIA 568B
Straight-through cable allows signals to pass “straight through” between terminations. Straight-through cables are used when connecting a PC to a Hub or Switch or when connecting Hubs together through their uplink ports.
Crossover cable: termination locations of transmit and receive wires on one end of cable reversed. Crossover cables are used when connecting a PC directly to another PC without going through a Hub or when connecting or “stacking” two hubs together through their data ports.
Installation tips to prevent Physical layer failures
See Pages in the text
Plenum and Non-Plenum Cabling (4:22)

66. Summary
Information can be transmitted via two methods: analog or digital
In multiplexing, the single medium is logically separated into multiple channels, or subchannels
Throughput is the amount of data that the medium can transmit during a given period of time
Baseband is a form of transmission in which digital signals are sent through direct current pulses applied to the wire
Noise is interference that distorts an analog or digital signal
Analog and digital signals may suffer attenuation
Cable length contributes to latency, as does the presence of any intervening connectivity device

67. Summary (continued)
Coaxial cable consists of a central copper core surrounded by a plastic insulator, a braided metal shielding, and an outer plastic cover (sheath)
Twisted-pair cable consists of color-coded pairs of insulated copper wires
There are two types of twisted-pair cables: STP and UTP
There are a number of Physical layer specifications for Ethernet networks
Fiber-optic cable provides the benefits of very high throughput, very high resistance to noise, and excellent security
Fiber cable variations fall into two categories: single-mode and multimode
Structured cabling is based on a hierarchical design that divides cabling into subsystems
The best practice for installing cable is to follow the TIA/EIA 568 specifications and the manufacturer’s recommendations

68. The End