Ch. 1 - Principles of Transmission
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187 terms
Terms | Definitions |
|---|---|
 An electrical conductor is | Any material that can carry an electric charge (1-2) |
| Most common electrical conductors are made from | Copper Copper covered steel High strength copper alloys Aluminum (not fiber or silver alloy) (1-2) |
| Sets the standard for comparing the conductivity of other metals | Annealed Copper (1-2) |
| Advantages of solid conductors | Less costly Less complex transmission Better transmission (1-4) |
| Annealed Copper conductivity % | 100% (1-2) |
| Corrosion resistance for: Aluminum | Good (1-3) |
| Oxidation resistance for: Aluminum | Poor (1-3) |
| Corrosion resistance for: High-strength alloys | Poor (1-3) |
| Ductility for: High-strength alloys | Better than copper (1-3) |
| Advantages of stranded conductors | More flexible Longer flex life Less susceptible to damage or crimping (not better transmission) (1-4) |
| Composite conductor is a term used to describe | Conductors constructed from non-traditional materials (1-4) |
| AWG stands for | American Wire Gauge (1-5) |
| Through usage and industrial standardization the AWG sizing system has become generally accepted in | North America (1-5) |
| Insulation, also called ___________ is used to isolate the flow of current by preventing the direct contact between conductors and its enviroment. | dielectric (1-5) |
| PVC (polyvinyl chloride) Insulated conductors = | Inside plant (1-5) |
| PE (polyethylene) Insulated conductors= | Outside plant (1-5) |
| Material which provides lower smoke and flame spread characteristics | FEP & ECTFE (Halar) (1-6) |
| FEP is a trademark of | Daikin America (1-6) |
| Teflon is a trademark of | E.I. du Pont 1-6 |
| Halar is a trademark of | Solvay Solexis 1-6 |
| Dielectric strength does what? | Measures the max. voltage that an insulation can withstand without breakdown 1-7 |
| Insulation Resistance (IR) is expressed in | Megohm per 1000' 1-7 |
| The main reason for twisting pairs of conductors is to minimize | Crosstalk & Noise 1-8 |
| Pair-to-Pair capacitance unbalance is is a measure of the | electrical field 1-8 |
| Mutual inductance is a measure of the | magnetic field 1-8 |
| Direction of pair twist | Counterclockwise 1-8 |
| Length of pair twist | 2-6 inches 1-8 |
| ____ twists tend to preserve their shape better in a cable | Tight 1-8 |
| Balanced twisted pair cable temp. attenuation concern above | 68 F 1-9 |
| High temps can be routinely encountered in | Exterior building walls Ceiling spaces Mechanical Rooms 1-9 |
| A temp. coefficient of _______% per degree Celsius is not uncommon for some CAT3 cables. | 1.5% 1-9 |
| Shielding effectiveness of a shield is determined by measuring the | surface transfer impedance 1-13 |
| Surface transfer impedance is measured in | ohms per foot 1-13 |
| A low-resistance _______ is the best possible shield. | solid wall metal tube (conduit) 1-14 |
| EM fields are expressed in | V/m (volts per meter) 1-14 |
| Foil shield rating | Excellent 1-15 |
| Shield effectiveness ratings: Poor ____, Fair _____, Good _____, Excellent ______ | Poor <20 dB, Fair 20-40 dB, Good 40-60 dB, Excellent >60dB 1-15 |
| The effectiveness of single-layer and multiple-layer braids against magnetic fields is _______. | Poor 1-15 |
| Permeability is the property of a | Magnetic substance (100% question) 1-15 |
| If a shield is not properly grounded its effectiveness is | reduced 1-16 |
| Drain wires are usually applied | longitudinally 1-16 |
| When to choose drain wire type | during cable selection 1-16 |
| An analog signal is in the form of a | wave (100% question) 1-17 |
| The most fundamental example of an analog signal is a | sinusoid 1-17 |
| Sinusoid is described by which three parameters | Amplitude Frequency Phase 1-18 |
| Human beings can hear | 20-20,000 Hz 1-18 |
| Voice circuits are limited to what range? | 300-3,400 Hz 1-18 |
| kHz Value | 1,000 Hz 1-18 |
| Phase is a description of the reference ______ | time 1-19 |
| The sinusoid theory developer | Joseph Fourier (take medicine for your sinusoids) 1-20 |
| An important property of a signal is its strength (power), which is often expressed in | Decibels 1-21 |
| If you have 1 watt of power on your input & 1 millowatt of power on your output, what is the total amount of power loss in dB? | 30db 1-21 |
| Power Ratios: +3dB ______, -3dB ______, +20dB ________ | +3dB doubles power, -3dB cuts in half, +20dB 100X (power increase) 1-21 |
| The three basic components of a telecom transmission system | Energy Medium Receiving device (except ex-splice, project managment, etc...) 1-23 |
| Same load resistance | Same impedance 1-24 |
| The 600 ohm impedance is preferred in | Private line or residential 1-24 |
| The 900 ohm impedance is preferred in | Central office 1-24 |
| Characteristic impedance for 22 awg & 26 awg cables | 600 ohms & 900 ohms 1-24 |
| Reflected signal= | echoe 1-24 |
| Round trip satellite delay | 1/4 s (1-24) |
| Speed of light | 186,000 miles per second (1-24) |
| _______ improves speech quality when placed at intervals along a cable. | Loading coils 1-25 |
| Common distance between loading points for D loading | 4,495' 1-25 |
| Common distance between loading points for H loading | 6,004' 1-25 |
| Two sinusoids whose sum is zero are considered | 180 degrees out of phase 1-22 |
| Data networks must have | QoS (quality of service) 1-26 |
| 802.3af | PoE 1-28 |
| 3 common interface options for use with IP telephony | IP telephone PC w/ IP telephony software Multifunctional devices w/ a wireless receiver 1-26 |
| 3 common implementation options for IP telephony architecture | Separate lines One line for everything (dual port phone or softphone) Wireless connection using AP's to connect 1-26 |
| 3 power source options for VoIP | VoIP Switches Midspan units Local power sources (not bridge) 1-28 |
| Maximum PoE output source level | 15.4 watts 1-28 |
| Digital signal changes | in discrete steps 1-29 |
| Analog to Digital conversion multistep process | Filtering Sampling Quantizing Companding (trick 4th step) 1-29 |
| Two types of companding | 1. A-Law - Europe 2. Mu-Law - United States 1-30 |
| Sampling theory developer | Harry Nyquist (sample nyquil) 1-30 |
| Analog to Digital signal process | Pulse Code Modulation (PCM) 1-30 |
| A PCM sampled value is assigned one of | 256 levels 1-30 |
| How many samples per second to digitize speech at 4hz? | 8,000 samples/s 1-30 |
| How many samples per second to digitize high fidelity speech or music at 16hz? | 32,000 samples/s 1-30 |
| CODECS = | conversion of speech 1-31 |
| When Time division multiplexing (TDM) is used: | Binary data from several different sources combine into a single composite bit stream Time slots are typically assigned to data by user addresses or codes (1-31) |
| Most popular form of TDM is: | statistical, that allows non-deterministic interleaving. (1-31) |
| TDM predetermined: | deterministic (1-31) |
| (8 b/s channel x 32 channels) x 8,000 frames/s | 2.048 Mb/s 1-33 |
| Two common methods of encoding | AMI & Manchester (Bi-Polar) 1-34 |
| BAUD | Modem 1-35 |
| ISDN basic rate | 160 kb/s 1-36 |
| ISDN primary rate | 1.544 Mb/s 1-36 |
| ATM (STS-1) or (OC-1) | 51.8 Mb/s 1-36 |
| ATM (STS-3) or (OC-3) | 155 Mb/s (STS1 x3) 1-36 |
| Fig 1.10 - AMI (alternate mark inversion) | spread apart buildings 1-37 |
| Fig. 1.11 - Manchester | bldgs close together in manhattan 1-37 |
| QAM | Quadrature Amplitude Modulation 1-39 |
| Transmission circuits are generally classified as | Simplex = 1 direction only Half-duplex = 1 direction at a time Full-duplex = both directions at a time 1-41 |
| Asynchronous | start & stop signals ineffcient (taxi) 1-42 |
| Synchronous | no start & stop bits efficient 1-42 |
| What does TDM do? | combines data 1-43 |
| Basic ISDN | Residential & Small Business (2) 64kb/s B channels & (1) 16 kb/s D channel capacity 160 kb/s (1-43) |
| Primary Rate ISDN North America | Large Business Users 23 B & 1 D channel operating @ 64kb/s. 1.544 Mb/s (1-43) |
| Primary Rate ISDN Europe | Large Business 30 B & 1 D channel 2.048 Mb/s (1-43) |
| ADSL 3 information channels | 1. Downstream channel 2. Medium speed duplex channel 3. POTS channel 1-45 |
| Baseband signaling | Composite/Component 1-49 |
| Color Pic | Red/Gree/Blue |
| Fig 1.16 Resistive Model | teeth 1-53 |
| Fig 1.18 Inductive Model | inductive field 1-55 |
| Crosstalk | Signal Interference 1-59 |
| NVP stated | % of speed of light 1-59 |
| NVP values for 100ohm range from | .56C-.74C 1-59 |
| Delay Skew | the difference in propagation delay between pairs in the same sheath 1-60 |
| Delay Skew shall not exceed | 45 nanoseconds 1-60 |
| Minimum NEXT loss - maximum attenuation = | ACR (attenuation-to-crosstalk ratio) 1-61 |
| Twisted pair impedance of 100ohms | @ 100 MHz 1-63 |
| NEXT loss occurs in | The near zone <66' 1-65 |
| 232-F Device | 150' 2 to 4 pairs 1-72 |
| DS1 rate | 1.544 Mb/s 2 pairs 1-72 |
| 100BASE-T4 & 10GBASE-T # of pairs | Both-4 pairs 100BASE-T4=100 Mb/s 10GBASE-T=10 Gb/s 1-72 |
| CAT3 shared sheath | maximum of 12 systems in a binder group 1-75 |
| Return loss | power of reflected signal 1-61 |
| (SNR) Signal to Noise Ratio | level of received signal & received noise 1-61 |
| Permanent link = | 90m or 295' TR to outlet 1-68 |
| 802.ab | 1000BASE-T 1-70 |
| Impedance matching devices | Baluns 1-76 |
| Balun | twisted pair to coax 1-76 |
| Max number of 10BASE-T systems that can share a binder group | 12 1-75 |
| Optical transmitter converts | electrical signal to optical signal 1-79 |
| A simple model of a telecommunications system has three parts: | Transmitter Receiver Medium (not tower, multiplexer) (1-79) |
| Optical receiver converts | optical signal to electrical signal 1-79 |
| Types of Optical Transmitters | 1. LED 2. CD 3. VCSEL 4. LD (not balun) 1-80 |
| Four nominal center wavelengths | 850 nm 1300 nm 1310 nm 1550 nm 1-80 |
| 50/125 NA (numerical aperture) | .20 1-83 |
| 62.5/125 NA (numerical aperture) | .275 1-83 |
| Four major types of transmitter light sources | Center wavelength Spectral width Emission pattern Modulation frequency 1-84 |
| Two major classifications of optical fiber are | SM & MM |
| Three classes of MM | OM1 OM2 OM3 1-91 |
| Two classes of SM | OS1 OS2 1-91 |
| OM1 size, bandwidth, distance, nm | 62.5/125 um mm 200 & 500 Mhz 1 kilometer 850 & 1300 nm (hook 62.5 & 200) 1-91 |
| OM2 size, bandwidth, nm | 50/125 um mm 500 & 500 Mhz 850 & 1300 nm (hook 50 & 500) 1-91 |
| OM3 size, bandwidth, nm | 50/125 um 2000 & 500 Mhz 850 & 1300 nm (hook 50 & 2000 & 500) 1-91 |
| OS1 size, bandwidth, nm | Singlemode 1310 & 1550 (hook 1310 & 1550) 1-91 |
| OS2 | Singlemode Multiplexing 1-91 |
| Twisted pair performance for CAT3, CAT5 & CAT5e, CAT6 | CAT3 = 16 mhz CAT5 & CAT5e = 100MHz CAT6 = 250 MHz 1-92 |
| Rise time | change from low power state to high power state (transmitters) 1-96 |
| Dispersion | broadening of a light pulse as it travels through the fiber 1-98 |
| Singlemode dispersion loss is expressed in | Picoseconds 1-98 |
| MM dispersion types | Chromatic & Modal (not singlemode) 1-99 |
| **MM fiber is best suited for premises applications where links are less than: | 6560' for data rates of 155 Mb/s or less 1804' for data rates of 1 Gb/s or less 984' for data rates of 10 Gb/s or less (1-102) |
| MM operating wavelength | 850nm 1st window 1300nm 2nd window 1-103 |
| Visible light | 400-700nm 1-106 |
| SM max attenuation outside & inside | Outside = 0.5 dB/km Inside = 1.0 dB/km 1-107 |
| Table 1.31 Max cable attenuation coefficient | Know this! 1-109 |
| Max permissible end-to-end system attenuation in a given link is determined by the | average transmitter power and the receiver sensitivity (1-113) |
| Power penalty for LED | 2dB 1-116 |
| Power penalty for LASERS | 3dB 1-116 |
| Repair margin | 2 splices 1-116 |
| Temperature may affect the loss of fiber as much as ________ | 2 dB (1-118) |
| *Fiber connector loss | .75 dB (1-118) |
| *Fiber splice loss | .3 dB (fusion & mechanical) (1-118) |
| Transmitter rates for OC1 - OC3 - OC12 | OC1 = 51.84 Mb/s - 672 voice channels OC3 = 155.52 Mb/s - 2016 voice channels OC12 = 8064 voice channels (1-122) |
| Fig. 1.30 Mux location | Q: where is the mux located? (1-123) |
| WDM uses a series of ________ to refract light and direct light pulses into a single optical fiber that carries the combined wavelengths. | lenses (1-124) |
| Number of channels in a DS1, DS2 & DS3 | DS1 = 24 DS2 = 96 DS3 = 672 (1-129) |
| The purpose of an optical transceiver is to | condition a signal (c&s) |
| The average splice loss for MM fusion splice is | 0.05dB (c&s) |
| Center wavelength values for commonly used optical fiber are | 850 nm, 1300 nm, 1550nm (c&s) |
| Units of inductance are measured in | Henries (c&s) |
| A balanced twisted pair permanent link consists of up to | 295' of horizontal cabling, including a connector at each end (c&s) |
| The relative length and uniformity of pair twists in a balanced twisted pair cable affect | capacitance unbalance & mutual inductance (c&s) |
| In general, characteristic impedance has both an | inductive & reactive component (c&s) |
| Balanced twisted-pair return loss measures | impedance mismatches in the cabling system (c&s) |
| ______ is a term used to describe the transmission of signals in both directions at the same time. | Full-duplex (c&s) |
| Optical fibers have bandwidth limitations because of _______ | dispersion (c&s) |
| Sept test - Which one is not an advantage of stranded copper conductors? | Better transmission (correct & my guess) More flexible Less susceptible to damage Longer flex life (1-4) |
| Sept test - The recommended maximum dB loss in fiber splice is _____ and in a mechanical connectors ________. | 0.3 & 0.75 (1-118) |
| Sept. test - If you had 1,000' of fiber on a reel how many Class ? circuits can you make? | (I said 1 because of the 900' rule) |
| The principal application for short wavelength lasers is: | Fibre Channel (1-85) |
| The max permissible end-to-end system attenuation in a given link is determined by: | The average transmitter power and the receiver sensitivity. (1-113) |
| Channel insertion loss is equal to the sum of the attenuation of the: | various components in the test channel, plus all the mismatch losses at cable and connector interfaces, and the increase in attenuation adjusted for temp. (1-65) |
| Which optical fiber transmitter has a center wavelength of 780 nm? | Short wavelength laser (1-88) (c&s) |
| An optical fiber system has enough power to operate over the passive portion of the link if: | The passive cable system attenuation/insertion loss is less than the link loss budget. (1-119) |
| If the system manufacturer does not specify the operating margin for an optical fiber system, use the value of: | 2dB for LED's and 3dB for lasers (1-116) |
| The characteristic parameters of optical fiber receivers are the: | Sensitivity Bit Error Rate (BER) Dynamic Range (1-89) (c&s) |
| The 8B/1Q4 PAM5 encoding scheme is specified in IEEE 802.3ab for use with: | 1000BASE-T (1-39) |
| At voice frequencies, the principal elements contributing to loss and phase distortion are: | conductor resistance and the mutual capacitance of the cable pair. (1-25) |
| A rating of 35dB indicates a cable shield effectiveness that is considered to be: | Fair (1-15) |
| An 8Mb/s ADSL downstream data rate over 24 AWG balanced twisted-pair can reach a max distance of: | 6,500' (1-46) |
| What is not a common method for used for line encoding: | Pulse coding (1-34) |
| What optical fiber transmitter type has center wavelengths of 1310nm and 1550nm? | Laser (LD) |
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