Download ppt - Differentiate between sine waves and square waves

Sep-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod4 – St. Lawrence College – Cornwall Campus – Clark slide 1



1. Differentiate between sine waves and square waves. 2. Define and calculate exponents and logarithms. 3. Define and calculate decibels. 4. Define basic terminology related to time, frequency,

and noise. 5. Differentiate between digital bandwidth and analog

bandwidth. 6. Compare and contrast noise levels on various types

of cabling. 7. Define and describe the affects of attenuation and

impedance mismatch. 8. Define crosstalk, near-end crosstalk, far-end

crosstalk, and power sum near-end crosstalk. 9. Describe how crosstalk and twisted pairs help reduce

noise. 10. Describe the ten copper cable tests defined in

TIA/EIA-568-B. 11. Describe the difference between Category 5 and

Category 6 cable.










Category 6 cable.


•They repeat the same pattern at regular intervals. •They occur naturally and change regularly over time. •No two adjacent points on a graph have the same value.


•They repeat the same pattern at regular intervals. •They repeat the flat pattern on both the top and bottom of the wave. •They do not continuously vary with time.










Category 6 cable.


•Three main numbering schemes


Power Formula used for gain or loss•light waves on optical fiber •radio waves in the air

The Power budget or Link budget(Watts,Volts,dB)










Category 6 cable.



Analyzing signals using an oscilloscope is called time-domain analysis, because the x-axis or domain of the mathematical function represents time.

In frequency-domain analysis, the x-axis represents frequency. An electronic device called a spectrum analyzer creates graphs for frequency-domain analysis.

More than one vertical input can show more than one wave simultaneously.


•Nearby cables which carry data signals (crosstalk)•Radio frequency interference (RFI), which is noise from other signals being transmitted nearby

•Electromagnetic interference (EMI), which is noise from nearby sources such as motors and neon lights •Laser noise at the transmitter or receiver of an optical signal (Not affected by electrical noise.)


Noise is added to the data signal.










Category 6 cable.


Examples of analog bandwidth values are 3 kHz for telephony, 20 kHz for audible signals, 5 kHz for AM radio stations, and 200 MHz for FM radio stations.

Digital bandwidth measures how much information can flow from one place to another in a given amount of time.

•Analog bandwidth refers to frequency range in Hz (cycles per second). •Digital bandwidth measures speed of the transmission in bits per second.










Category 6 cable.


•braided conductive •foil-screened(good shielding )


•protect one pair of wires within the cable from noise generated by electrical signals on another pair of wires •protect the data signal from external sources of noise •eliminate signal loss by keeping the transmitted signal confined to the cable



•light/no light •increasing/decreasing light intensity

•Low attenuation•No electrical interference










Category 6 cable.


Factors that contribute to attenuation in copper media•long cable lengths •defective connectors •energy leaks through the insulation of the cable


•The resistance of the copper cable converts some of the electrical energy of the signal to heat. •Signal energy is also lost when it leaks through the insulation of the cable and by •Impedance caused by defective connectors.

•Impedance is a measurement of the resistance of the cable to alternating current (AC) and is measured in ohms. •The normal, or characteristic, impedance of a Cat5 cable is 100 ohms. •If a connector is improperly installed on Cat5, it will have a different impedance value than the cable.•This is called an impedance discontinuity or an impedance mismatch.











Category 6 cable.


•no electrical signals •no generation of electromagnetic waves

Fiber has no Crosstalk (Xtalk)

•Crosstalk (xtalk) is another form of noise



•CAT 5e & 6c


Equal Level Far End Cross Talk (ELFEXT)



openshort











Category 6 cable.


•Wire map •Insertion loss •Near-end crosstalk (NEXT) •Power sum near-end crosstalk (PSNEXT) •Equal-level far-end crosstalk (ELFEXT) •Power sum equal-level far-end crosstalk (PSELFEXT) •Return loss •Propagation delay •Cable length •Delay skew

Cable testing standards












Category 6 cable.


A pulse is a deliberate, fixed disturbances of predictable duration used to…•Measure propagation delay (delay skew) to determine the value of the data being transmitted •Find discontinuities (reflections, jitter)•Measure transmission length





1. Waves are energy traveling from one place to another, and are created by disturbances. All waves have similar attributes such as amplitude, period, and frequency.

2. Sine waves are periodic, continuously varying functions. Analog signals look like sine waves.

3. Square waves are periodic functions whose values remain constant for a period of time and then change abruptly. Digital signals look like square waves.

4. Exponents are used to represent very large or very small numbers. The base of a number raised to a positive exponent is equal to the base multiplied by itself exponent times. For example, 103 = 10x10x10 = 1000.

5. Logarithms are similar to exponents. A logarithm to the base of 10 of a number equals the exponent to which 10 would have to be raised in order to equal the number. For example, log10 1000 = 3 because 103 = 1000.

6. Decibels are measurements of a gain or loss in the power of a signal. Negative values represent losses and positive values represent gains.


7. Time-domain analysis is the graphing of voltage or current with respect to time using an oscilloscope. Frequency-domain analysis is the graphing of voltage or power with respect to frequency using a spectrum analyzer.

8. Undesirable signals in a communications system are called noise. Noise originates from other cables, RFI, and EMI. White noise affects all frequencies, while narrowband interference affects only a certain subset of frequencies.

9. Analog bandwidth is the frequency range that is associated with certain analog transmission, such as television or FM radio.

10. Digital bandwidth measures how much information can flow from one place to another in a given amount of time. Its units are in various multiples of bits per second.

11. Most LAN problems occur at the physical layer. The only way to prevent or troubleshoot many of these problems is through the use of cable testers.

12. Proper cable installation according to standards increases LAN reliability and performance.


13. Copper media is available in shielded and unshielded forms. Unshielded cable is more susceptible to noise.

14. Signal degradation is due to various factors such as noise, attenuation, impedance mismatch, and several types of crosstalk. These factors cause decreased network performance.

15. The TIA/EIA-568-B standard specifies ten tests that a copper cable must pass if it will be used for modern, high-speed Ethernet LANs.

16. Optical fiber must also be tested according to networking standards.

17. Category 6 cable must meet more rigorous frequency testing standards than Category 5 cable.



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