Transmitting Bits

Topics: Cable, Twisted pair, Ethernet Pages: 11 (2211 words) Published: December 14, 2014
Dennis Thrane
NT 1210
Unit 4 Lab
Exercise 4.1.1 Why are standards so important for NICs, connectors, and media? Use your textbook and Internet research to justify your answer. The physical level determines how the 0 and 1 bits are identified. So both ends need to know the voltage range for a 1 and for a 0. If they used different values then the data would be lost, or the voltage at the destination may be so high that the current delivered to the destination could destroy the receiver. The NIC has the MAC address which has to be unique on each Local Area Network. When a frame is sent the format of the frame has to be understood by the destination NIC. If the format of the frames were different then the two devices could not communicate. Exercise 4.1.2 The voltage for registering a bit of 1 on Ethernet can be as low as 2.5 volts or even 1 volt. Why is this so low when the capacity for transmitting electricity on the copper wire is so high? Use your textbook and Internet research to support your answer. Copper wire is used to power appliances which use more current. The difference is between signal circuits and power circuits. Signal circuits operate at extremely low current levels and use digital logic voltage levels (less than 5 VDC). Power circuits on the other hand require larger amounts of current to operate electrical devices such as motors, heating units, etc. Exercise 4.1.3 What are some applications of shielded copper cable? Why is the more expensive shielded cable used in these situations? Use your textbook or Internet research to support your answer. Microphones, PA systems, Audio cables, Power cables, and RG-6 Cables used for television. There are three reasons, that I can think of, to use shielded cable instead of unshielded. Radio Frequency Interference (RFI) was the earliest interference engineers had to deal with.  Early radio signals easily found their way into devices.  Coaxial cables and shielded twisted pairs using copper can eliminate most of this type of interference. Electromagnetic Interference (EMI) comes more into play today with high power transmission lines, higher magnetic fields, such as MRI machines in hospitals, and other high power applications.  Copper may not offer much resistance to higher magnetic fields; therefore the use of magnetic materials such as high permeable irons may be required. And lastly you have Electro Magnetic Pulse (EMP) is produced by the detonation of nuclear devices.  When the Hydrogen Bombs were tested in the 1950s at Bikini Atoll in the south pacific, circuit breakers at power stations in Hawaii were tripped by the EMP wave from the detonation.  Critical military and civilian circuits have to be protected from an EMP condition.  These shields require the use of both high and low permeable materials to reduce the effect of an EMP.

Exercise 4.1.6 Briefly describe the layered construction of a coaxial cable from the inner core to the outer insulation. Use your textbook and Internet research to compose your answer. A coaxial cable starts with a copper wire in the core, which is surrounded by a dielectric insulator. These are then wrapped by a thin metallic shield. And finally it is protected by a plastic jacket. Exercise 4.1.7 Based solely on the distance limitation of UTP cable, what should you guarantee about any network you plan for UTP cable? Use your textbook and Internet research to justify your answer. You should always guarantee that all devices are under 100 meters away from each other so that you can prevent attenuation. Exercise 4.1.8 What type of cable is necessary for each connection in Figure 4- 2: straight or crossover? You can assume that S1 and S2 do not have the ability to resolve crossovers ( called Auto- MDIX). Use your textbook and Internet research to compose your answer. S1-A(straight) S1-B (straight) S1-C (straight) C-D (crossover) S1-S2 (multimode fiber) S2-E (straight) S2-F (straight) S2-G (multimode fiber) F-G (crossover)...
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