User:Itpastorn/dko/ccna1-3.1-4
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Cable Testing
Overview CCNA 1 - Module 4 (3.1)
- Sine waves and square waves
- Exponents and logarithms
- Decibels on networking media (not audio)
- Terminology related to time, frequency, and noise
- Digital bandwidth and analog bandwidth
- Noise levels
- Attenuation and impedance mismatch
- Define crosstalk, near-end crosstalk, far-end crosstalk, and power sum near-end crosstalk
- Twisted pair wiring and noise
- The ten copper cable tests defined in TIA/EIA-568-B
- Category 5 and Category 6
Frequency-Based Cable Testing
[edit]- Frequency, measured in Hz
- Period, the inverse of frequency
- Wavelength
- Amplitude
Sine waves and square waves
[edit]Exponents and logarithms
[edit]Three important number systems:
- Binary
- Base 2
- Decimal
- Base 10
- Hexadecimal
- Base 16
- Easier to use 109 than 1000000000.
- "Logarithms with 10 as a base are called common logarithms."
dB = 10 log10 (Pfinal / Pref)
dB = 20 log10 (Vfinal / Vref)
Time and frequency of signals
[edit]"Characters, words, pictures, video, or music can be represented electrically by voltage patterns on wires and in electronic devices..." "these voltage patterns can be converted to light waves or radio waves... and back"
- Oscilloscope - "time-domain analysis"
Analog and digital signals
[edit]- Fourier synthesis of a square wave
Noise in time and frequency
[edit]Noise = undesirable signal
Sources
- Nearby cables
- RFI
- EMI (same article as RFI on Wikipedia)
- Laser noise at the transmitter or receiver
Frequencies affected:
- White noise = all frequencies
- Narrowband interference = small spectrum, but usually stronger
- Digital broadband = very high speed
- >= 2 Mbps both upstream and downstream, according to Bredbandsutredningen
- Only in marketing: Anything that is not a modem - which is false marketing!
- Analog broadband, opposite of baseband
Signals and Noise
[edit]Signals over copper and fiber optic cables
[edit]Copper
- signal ground. Important that devices to be "properly grounded"
- Two basic types of cables (covered in the last module):
- Shielded: Coaxial, STP, ScTP
- Unshielded: UTP
Fiber
- Less attenuation
- RFI and EMI is no problem
- Grounding seldom a problem
Attenuation and insertion loss on copper media
[edit]Sources of noise on copper media
[edit]Types of crosstalk
[edit]Cable testing standards
[edit]Other test parameters
[edit]Time-based parameters
[edit]Testing optical fiber
[edit]A new standard
[edit]Extra topics (in addition to CCNA)
[edit]Additional resorces (besides Wikipedia)
[edit]- Module 4 exam questions at Learn Networking
- The basics of Cable Testing at Learn Networking
- A manufacturers site with cable categories
- De-Mystifying Cabling Specifications From 5e to 7A
- Crosstalk explained at Siemon's site
- Guide to Alien Crosstalk in Network Cabling Systems