Fritz Dorcelus _ Physical Networking
Cable Structure
Week 3 assignment
1-What are the most common cables used today?
Unshielded twisted-pair (UTP), shielded or screened twisted-pair (STP or ScTP), coaxial, and fiber-optic (FO)
2. Simply installing STP cabling does not guarantee that you will improve a cable’s immunity EMI or reduce the emissions from the cable. What are several critical conditions must be satisfied to achieve good shield performance? * The shield must be electrically continuous along the whole link. * All components in the link must be shielded. No UTP patch cords can be used. * The shield must fully enclose the pair, and the overall shield must fully enclose the core. Any gap in the shield covering is a source of EMI leakage. * The shield must be grounded at both ends of the link, and the building grounding system must conform to grounding standards (such as J-STD-607-A).
3. What are the distinct advantages of fiber optic?
• Transmission distances are much greater than with copper cable.
• Bandwidth is dramatically higher than with copper.
• Fiber optic is not susceptible to outside EMI or crosstalk interference, nor does it generate EMI or crosstalk.
• Fiber-optic cable is much more secure than copper cable because it is extremely difficult to monitor, “eavesdrop on,” or tap a fiber cable.
4. Cable bandwidth is a function of three interrelated, major elements. What are these major elements?
Distance, Frequency, and Signal-level-to-noise-level ratio (SNR)
5. what is the operating frequency of the 100 Base T Ethernet LAN system?
31.25 MHZ
6. What unit of measurement is a tenfold logarithmic ratio of power output to power input?
Decibel
7. what electrical components contribute to attenuation?
8. List the different types of crosstalk? Crosstalk is a disturbance caused by the electric or magnetic fields of one telecommunication signal affecting a signal in an adjacent circuit. In an telephone circuit, crosstalk can result in your hearing part of a voice conversation from another circuit. The phenomenon that causes crosstalk is called electromagnetic interference (EMI). It can occur in microcircuits within computers and audio equipment as well as within network circuits. The term is also applied to optical signals that interfere with each other.

Near-End Crosstalk (NEXT)
When the crosstalk is detected on the same end of the cable that generated the signal, then near-end crosstalk has occurred. NEXT is most common within 20 to 30 meters (60 to 90 feet) of the transmitter
Far-End Crosstalk (FEXT)
Far-end crosstalk (FEXT) is similar to NEXT except that it is detected at the opposite end of the cable from where the signal was sent. Due to attenuation, the signals at the far end of the transmitting wire pair are much weaker than the signals at the near end.
The measure of FEXT is used to calculate equal-level far-end crosstalk (ELFEXT). More FEXT will be seen on a shorter cable than a longer one because the signal at the receiving side will have less distance over which to attenuate

Equal-Level Far-End Crosstalk (ELFEXT)
Equal-level far-end crosstalk (ELFEXT) is the crosstalk coupling between cabling pairs measured at the end of the cable opposite to the end of the signal source, taking into account signal loss. ELFEXT is calculated, not measured, by subtracting the attenuation of the disturber pair from the far-end crosstalk (FEXT) on the disturbed pair. The calculation describes the ratio of disturbance to the level of the desired signal; it is another indication of signal-to-noise ratio. Another way of looking at it is that the value represents the ratio between the strength of the noise due to crosstalk from end signals compared to the strength of the received data signal. You could also think of ELFEXT as far-end ACR (attenuation-to-crosstalk ratio, described later in this chapter).
Each pair-to-pair combination is measured, as the attenuation on each pair will be slightly different. If the ELFEXT value is very high, it may indicate that either excessive attenuation has occurred or that the far-end crosstalk is higher than expected.

9. Which of the following organizations is part of the US government? Federal communications commission (FCC)
Institute of Electrical and Electronic Engineers (IEEE)
National Fire Protection Association (NFPA)
Underwriters laboratories.(UL)
10. when it comes to cabling what is the national fire protection Associate responsible for?
Generally speaking, the following codes govern communications cables:
NFPA 90A-Standard for Air Conditioning and Ventilation Equipment
NFPA 90A is responsible for plenum spaces in buildings. In the 2002 Edition, this standard sets requirements for flame, smoke and fuel load in the following section: 4.3.10.2.6-"All materials exposed to the airflow shall be non-combustible or limited combustible and have a maximum smoke developed index of 50..." (From the 2002 edition). This refers to NFPA's smoke index rating and a flame spread index rating.
Under this code, combustible cables are allowed as an exception.
When designing network infrastructure to a standard of protection as opposed to minimal code compliance, it is advisable to design to the NFPA 90A primary requirement that all materials installed and exposed to environmental airflow be noncombustible or limited combustible as opposed to compliance with wire and cable exception. LCC cabling meeting the requirements of NFPA 5000 model building code, and NFPA 13 model sprinkler code for limited combustible materials allows it to be installed in virtually any noncombustible building construction without the need for additional fire protection (sprinklers or noncombustible conduit).
11.what is a backbone cabling and where is it used?
The part of your network that ties different departmental networks into a single whole. The backbone carries the bulk of the network traffic and must be designed accordingly.
The backbone cabling system provides interconnections between telecommunications rooms, equipment rooms, main terminal space, and entrance facilities. It includes backbone cables, intermediate and main cross-connects, mechanical terminations, and patch cords or jumpers used for backbone-to-backbone cross-connections. The backbone also extends between buildings in a campus environment.
12. A telecommunications room can sometimes be referred as ?
An enclosed area housing telecommunications cabling, patch panels, and interconnections, sometimes referred to as a “telecommunications closet.” Generally, one or more telecommunications rooms on each floor of a building serve as distribution points for communications cabling installed to locations on that floor. These intermediate rooms also serve as a demarcation point between the horizontal cabling for end-users and the building’s backbone cabling system.
13. What are the three commonly used network architectures used today?

14.Which of the following is true about 10 Base-T networking?
10 Base-T requires 2 pairs of an eight-pin modular jack.
The minimum length of a 10 base-T cable is 2 feet.
There is no maximum length for a 10 base –t Cable.
All of the above.

15. the 10 Base-T4 specifications was developed as part of the 100 Base-T specification so that the existing ________ could also support fast Ethernet.
16. ATM uses high-speed cell switching technology that can handle data and real time voice and video.
True.
False.
17. what standards organization does the National electricity code sponsor?
18. what does NEC article 250 covers?
19. Acording to the NEC, article 800,100, primary protectors shall be grounded:
a. If a separate grounding is installed for communications, it must be bonded to the electrical electrode sytem with a conductor.
b. the grounding conductor shall be insulated and llisted as suitable for the purpose.
c. the grounding conductor shall be attached to the grounding electrode.
d. all of the above.
20. Article 800.154 “installation of communications wires, cables and equipment” states that the accessible portion of abandoned category 1 and 3 type cable shall not be permitted to remain because category 1 and 3 type cables: a. Are difficult to properly ground b. Can not support the Bandwidth of a new system c. Do not have NEC copper Communications-Cable Markings d. Have inadequate flame ratings.
21. Which of the following is an advantage of knowing and following the electrical and building codes?
a. it helps protect the building’s occupants.
b. it helps when working with electricians and contractors.
c. it helps when working with local, city, county or state officials.
d. All of the above.