CHAPTER 2 Flashcards
EMC
ELECTROMAGNETIC COMPATIBILITY
ABILITY OF A DEVICE, EQUIPMENT, OR SYSTEM TO OPERATE PROPERLY IN ITS INTENDED ELECTROMAGNETIC ENVIRONMENT WITHOUT INTRODUCING SIGNIFICANT ELECTROMAGNETIC INTERFERENCE (EMI) INTO THE ENVIRONMENT.
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EMI
ELECTROMAGNETIC INTERFERENCE
THE TRANSFER OF ELECTROMAGNETIC ENERGY FROM ONE DEVICE OR SYSTEM TO ANOTHER DEVICE OR SYSTEM OPERATING IN THE SAME ENVIRONMENT THAT CAUSES INTERFERENCE WITH NORMAL OPERATION OF THE DEVICES OR SYSTEMS.
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ELECTROMAGNETIC EMISSON
THE PHENOMENOM BY WHICH ELECTROMAGNETIC ENERGY EMANATES FROM A SOURCE. EMISSIONS CAN BE EITHER RADIATED OR CONDUCTED WHEN COUPLED INTO A GIVEN DISTURBED CIRCUIT. SUCH EMMSISIONS MAY BE DIVIDED INTO TWO CATEGORIES: INTENTIONALLY EMITTED SIGNALS AND UNITENTIONAL EMMISIONS.
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ELECTROMAGNETIC IMMUNITY
THE ABILITY OF A DEVICE, EQUIPMENT, SYSTEM TO PERFORM WITHOUT DEGREDATION IN THE PRESENCE OF AN ELECTROMAGNETIC DISTURBANCE.
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EMR
ELECTROMAGNETIC RADIATION
RADIATION COMPOSED OF OSCILLATING ELECTRICAL AND MAGNETIC FIELDS AND PROPOGATED THROUGH A MEDIUM.
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ESD
ELECTROSTATIC DISCHARGE
THE SUDDEN FLOW OF ELECTRICITY BETWEEN TWO ELECTRICALLY CHARGED OBJECTS CAUSED BY CONTACT.
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GROUNG LOOP
TWO PARALLEL PATHS THAT HAVE IDENTICAL CONDUCTIVE TERMINATIONS TO TWO SEPERATE GROUNDING REFERENCES.
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RFI
RADIO FREQUENCY INTERFERENCE
THE DEGREDATION OF A DESIRED SIGNAL AT THE RECEPTOR END CAUSED BY RADIO FREQUENCY DISTURBANCE WITHIN THE RADIO FREQUENCY SYSTEM WHICH IS USUALLY COMPRISED IN TE FREQUENCY RANGE THAT INCLUDES LF, MF, HF, AND VHF.
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TWO DEVICES ARE USING OVERLAPPING OPERATIONAL FREQUENCIES WITHIN THE SAME EM ENVIRONMENT. WHAT IS THE LIKELY AFFECT ON THE POTENTIAL FOR EMI IN THIS ENVIRONMENT?
THE POTENTIAL FOR EMI IS LIKELY TO INCREASE UNDER THESE CONDITIONS.
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NAME 4 MECHANISMS THAT CAN CREATE COUPLING BETWEEN TWO CIRCUITS OR SYSTEMS.
- CONDUCTIVE COUPLING
- INDUCTIVE COUPLING
- CAPACITIVE COUPLING
- ELECTROMAGNETIC COUPLING
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WHAT TYPE OF COUPLING MAY OCCUR WHEN A COMMON AC BRANCH CIRCUIT IS SHARED BETWEEN TWO DEVICES?
CONDUCTIVE COUPLING
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WHAT CAUSES INDUCTIVE COUPLING?
MAGNETIC FIELDS
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WHAT CAUSES CAPACITIVE COUPLING?
ELECTRIC FIELDS
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NAME 3 ESSENTIAL ELEMENTS OF ANY EMC PROBLEM
- SOURCE OF AN EMI ELECTROMAGNETIC ENERGY TRANSFER
- SUSCEPTIBLE DEVICE OR SYSTEM THAT CANNOT PERFORM AS DESIGNED, CONFIGURED, OR PROGRAMMED BECASUE OF THE EMI EVENT.
- COUPLING PATH THAT PROMOTES THE DISTURBANCE
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NAME 8 EXAMPLES OF EMR
- GAMMA RAYS
- X-RAYS
- UV LIGHT
- VISIBLE LIGHT
- IR RADIATION
- RADAR
- MICROWAVES
- RADIOWAVES
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WHAT IS THE SPEED OF LIGHT?
300,000 km/s (186,300 mi/s) IN A VACUUM
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NAME THE 2 CHARACTERISTICS THAT ARE USED TO DISTINGUISH ELECTECTROMAGNETIC WAVES.
- WAVELENGTH (EXPRESSED IN METERS)
- FREQUENCY (EXPRESSED IN HERTZ)
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HOW MANY FREQUENCY BANDS ARE RECOGNIZED BY THE ITU?
12
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TRUE OR FALSE
VISIBLE LIGHT REPRESENTS THE LARGEST PORTION OF THE ELECTROMAGNETIC SPECTRUM.
FALSE, VISIBLE LIGHT REPRESENTS ONLY A SMALL PORTION OF THE ELECTROMAGNETIC SPECTRUM.
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NAME THE 3 PRIMARY PATHS THROUGH WHICH CONDUCTED COUPLING MAY AFFECT ELECTRONIC DEVICES.
- INPUT SIGNAL LINES
- OUTPUT SIGNAL LINES
- UTILITY OR PREMISES ELECTRICAL POWER DISTRIBUTION
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NAME THE 4 PRIMARY CONDITIONS THAT ALLOW RADIATED INTERFERENCE TO ENTER ELECTRONIC DEVICES
- PROXIMITY TO INTERFERING SOURCES
- MISSING OR INADEQUATE GASKETS/ENCLOSURES
- MISSING OR INADEQUATE BONDING AND GROUNDING SYSTEM COMPONENTS.
- MISSING OR INADEQUATE DEVICE OR CABLE SHIELDING
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TRUE OR FALSE
ELECTRICAL CODES DO NOT GENERALLY PROVIDE FOR EMC
TRUE, ELECTRICAL CODES DO NOT PROVIDE FOR EMC.
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WHAT IS AN ELECTROMAGNETIC FIELD?
AN AREA OF ENERGY THAT SURROUNDS ELECTRICAL DEVICES
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WHAT TYPE OF CHARGE CREATES AN ELECTRIC FIELD?
STATIONARY
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WHAT TYPE OF CHARGE CREATES AND MAGNETIC FIELD?
MOVING (ELECTRICAL CURRENTS)
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NORMALLY, IT IS NOT PRACTICAL TO CONTROL EXTERNAL SOURCES OF EMI. WHAT METHODS SHOULD THE ICT DESIGNER USE TO ADDRESS THIS TYPE OF EMI INSTEAD?
REVERT TO METHODS THAT PROMOTE SYSTEM IMMUNITY.
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WHAT IS A RELIABLE AND EFFECTIVE TECHNIQUE FOR MITIGATING THE EFFECTS OF RADIO FREQUENCY INTERFERENCE ON TELEPHONE SETS?
DEPLOYING SHIELDED OR SCREENED STRUCTURED CABLING SYSTEMS IN CONCERNED AREAS.
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WHY IS IT DIFFICULT TO TO DETERMINE A DEVICES EMC?
BECAUSE ITS VALUE IS RELATIVE TO THE ENVIRONMENTIN WHICH IT WILL OPERATE.
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NAME 2 COMPONENTS OF EMC.
- EMISSION
- IMMUNITY
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WHAT UNITS OF MEASURE ARE USED TO DESCRIBE MAGNETIC FIELDS?
AMPERES PER METER
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WHAT FREQUENCY SPECTRUM IS TYPICALLY USED FOR MEASURING CONDUCTED INTERFERENCE?
100 kHz TO 30 MHz
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WHAT FREQUENCY SPECTRUM IS TYPICALLY USED FOR MEASURING RADIATED INTERFERENCE?
30 MHz TO 5 GHz
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HOW IS IMMUNITY TO RADIATED EMISSIONS DETERMINED?
BY EXPOSING THE DEVICE BEING MEASURED TO A SPECIFIED ELECTROMAGNETIC FIELD AND MONITORING ITS PERFORMANCE.
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NAME 4 TYPES OF RADIATED INTERFERENCE MEASUREMENTS
- ANECHOIC CHAMBER
- TEM CELL
- REVERBERATING CHAMBER
- GHz TEM CELL
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NAME 3 TYPES OF CONDUCTED INTERFERENCE MEASUREMENTS.
- CM AND DM INTERFERENCES
- CONDUCTED ELECTROMAGNETIC NOISE AND POWER SUPPLY LINES
- CONDUCTED EMI FROM EQUIPMENT
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WHAT IS THE ACCEPTANCE CRITERIA FOR FIELD INTENSITY FOR TELECOMMUNICATIONS EQUIPMENT AND CABLING?
3 V/m
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WHAT MAJOR PARAMETERS ARE LIKELY TO FAIL FIELD TESTING ON A TRIAL LINK IF ELEVATED LEVELS OF EMI ARE PRESENT?
CROSSTALK (SUCH AS NEXT AN ANEXT)
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WHAT DESIGN FACTOR COULD CAUSE EMI ON A TELECOMMUNICATIONS SYSTEM?
EXCESSIVE LENGTHS OF UNSHIELDED CABLES BETWEEN ROOMS OF BUILDINGS.
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NAME 4 DESIGN FACTORS THAT COULD CAUSE EMI ON A SITES TELEPHONE DISTRIBUTION SYSTEM.
- UNBALANCED CABLING
- INCORRECT OR MISSING PRIMARY PROTECTORS
- INCOMPATIBLE SECONDARY PROTECTORS
- INCORRECT OF MISSING GROUNDS.
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WHAT IS THE AIM OF EMC?
TO ENSURE THAT EQUIPMENT ITEMS OR SYSTEMS WILL NOT INTERFERE WITH OR PREVENT EACH OTHERS OPERATION THROUGH SPURIOUS EMISSION AND ABSORPTION OF EMI
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WHAT IS THE FOCUS OF EMC?
TO CONTROL EMI
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TRUE OR FALSE
THE EMI PROBLEM IS ALWAYS A CIRCUIT.
TRUE, THE EMI PROBLEM IS ALWAYS A CIRCUIT.
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TRUE OR FALSE
EMI IS OFTEN EASY TO REMEDY ONCE THE ROOT CAUSE IS IDENTIFIED.
TRUE, EMI IS OFTEN EASY TO REMEDY ONCE THE ROOT CAUSE IS IDENTIFIED.
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NAME 3 COMMON SOURCES OF EMI PROBLEMS
- CONDUCTED AND RADIATED EMISSION SOURCES
- TRANSFER OF PROPOGATION SOURCES
- RECEIVING OR RECEPTOR ELEMENTS
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NAME 2 NATURAL SOURCES OF EMI.
- ATMOSPHERIC ELECTRICITY
- COSMIC RADIATION OR GEOMAGNITISM DISTRUBANCES
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NAME 6 MAN MADE SOURCES OF EMI
- ELECTRICAL POWER
- COMMUNICATIONS ELECTRONICS
- RELAY COMMUICATIONS
- TOOLS AND MACHINES
- IGNITION SYSTEMS
- INDUSTRIAL AND CONSUMER EQUIPMENT OR PRODUCTS
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NAME 3 METHODS USED TO SUPPRESS OR PREVENT UNWANTED SIGNALS
- SHIELDING
- FILTERING
- BONDING AND GROUNDING OF CABLE SHIELDS AND EQUIPMENT
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NAME 3 TYPES OF ESD.
- DISCHARGE SPARK IN THE AIR
- RADIATED EFFECTS OF ESD.
- CONTACT DISCHARGE
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HOW MANY LEVELS OF IMMUNITY ARE USED TO DESCRIBE ESD?
4
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 1 IMMUNITY FOR CONTACT DISCHARGE?
2 kV
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 2 IMMUNITY FOR CONTACT DISCHARGE?
4 kV
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WHAT VOLTAGE IS ASSOCIATED WITH LEVEL 3 IMMUNITY FOR CONTACT DISCHARGE?
6 kV
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 4 IMMUNITY FOR CONTACT DISCHARGE?
8 kV
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 1 IMMUNITY FOR AIR DISCHARGE?
2 kV
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WHAT VOLTAGE IS ASSOCIATED WITH LEVEL 2 IMMUNITY FOR AIR DISCHARGE?
4 kV
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 3 IMMUNITY FOR AIR DISCHARGE?
8 kV
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WHAT VOLTAGE LEVEL IS ASSOCIATED WITH LEVEL 4 IMMUNITY FOR AIR DISCHARGE?
15 Kv
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WHAT IS THE ELECTROSTATIC DISCHARGE SUSCEPTIBILITY VOLTAGE RANGE FOR VERTICAL METAL OXIDE SEMICONDUCTORS?
30 TO 1800 V
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WHAT IS THE ELECTROSTATIC DISCHARGE SUSCEPTIBILITY VOLTAGE RANGE FOR OPERATIONAL AMPLIFIERS?
190 TO 2500 V
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WHAT IS THE ELECTROSTATIC DISCHARGE SUCEPTIBILITY RANGE FOR RESISTORS?
300 TO 3000 V
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WHAT CAN CAUSE A TELECOMMUNICATIONS CABLE TO STORE ENERGY AND THEN DISCHARGE IT AS ESD?
MUTUAL CAPACITANCE
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WHAT IS THE RELATIONSHIP BETWEEN THE CATEGORY OF A BALANCED CABLE AND ITS ABILITY TO STORE ENERGY?
THE HIGHER THE CABLE CATEGORY, THE LOWER ITS ABILITY TO STORE ENERGY.
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WHAT IS THE MUTUAL CAPACITANCE RANGE FOR CATEGORY 3 CABLE?
64 TO 66 pF/m
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WHAT IS THE MUTUAL CAPACITANCE RANGE FOR CATEGORY 5e CABLE?
44 TO 49 pF/m
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WHAT IS THE MUTUAL CAPACITANCE RANGE FOR CATEGORY 6 CABLE?
44 TO 46 pF/m
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WHAT IS THE MUTUAL CAPACITANCE RANGE FOR CATEGORY 6A CABLE?
43 TO 45 pF/m
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WHAT IS THE MUTUAL CAPACITANCE VALUE FOR CATEGORY 8 CABLE?
1.2 pF/m
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NAME THE 2 TYPES OF UNWANTED SIGNALS ON A CABLE IN AN EMI EVENT/
- COMMON MODE (CM)
- DIFFERENTIAL MODE (DM)
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WHICH TYPE OF UNWANTED SIGNAL INVOLVES A GROUND PLANE?
COMMON MODE (CM)
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WHEN DOES A CM SIGNAL BECOME EVIDENT?
ONLY WHEN MEASURED AGAINST A REFERENCE GROUND
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HOW DO CM UNWANTED SIGNALS DIRECTLY AFFECT EQUIPMENT OPERATION?
BY ENTERING THE EQUIPMENT AND CAUSING LOGICAL ERRORS
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WHAT IS THE PRIMARY WAY THAT DM NOISE AFFECTS EQUIPMENT?
BY CORRUPTING TRANSMITTED SIGNALS ON A BALANCED CIRCUIT.
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WHAT IS THE RELATIONSHIP BETWEEN THE TRANSMISSION RATE OF CABLING AND INTERFERENCE?
THE HIGHER THE TRANSMISSION RATE, THE HIGHER THE EFFECT OF THE INTERFERENCE.
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WHAT TERM DESCRIBES TWO PARALLEL PATHS THAT HAVE IDENTICAL CONDUCATIVE TERMINATIONS TO TWO SEPERATE GROUNDING REFERENCES?
GROUND LOOP
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TRUE OR FALSE
THE EARTH IS ALWAYS ONE OF THE PARALLEL PATHS BETWEEN THE GOUNDING REFERENCES IN A GROUND LOOP.
FALSE. THE EARTH IS OFTEN, BUT NOT ALWAYS, ONE OF THE PARALLEL PATHS BETWEEN THE GROUNDING REFERENCES IN A GROUND LOOP.
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WHAT IS THE PURPOSE OF ELECTROMAGNETIC SHIELDING?
TO REDUCE OR PREVENT COUPLING OF UNDESIRED RADIATED ELECTROMAGNETIC ENERGY INTO A GIVEN SYSTEM TO ENABLE IT TO OPERATE PROPERLY IN ITS ELECTROMAGNETIC ENVIRONMENT.
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NAME THE 2 APPROACHES TO USING CABLE SHIELDING AS AN EMI MITIGATION TECHNIQUE.
- LOW FREQUENCY NOISE MITIGATION
- HIGH FREQUENCY NOISE MITIGATION
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WHAT ABSORBS THE MAJORITY OF EMI EFFECTS AT LOWER FREQUENCIES?
CABLE TWISTS
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WHAT PART OF THE CABLE ABSORBS THE MAJORITY OF EMI EFFECTS AT HIGHER FREQUENCIES?
THE CABLE SHIELD.
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HOW DOES PASSING THROUGH A MEDIUM AFFECT THE AMPLITUDE OF AN ELECTROMAGNETIC WAVE?
IT DECREASES EXPONENTIALLY.
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WHAT PARAMETER BEST DESCRIBES THE CABLE SHIELDING RESPONSE?
SHIELDING EFFECTIVENESS
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WHAT IS TRANSFER IMPEDANCE?
A RATIO OF THE VOLTAGE INDUCED ON THE INSIDE SURFACE OF THE SHIELD TO THE CURRENT FLOWING ON ITS OUTSIDE SURFACE.
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WHAT TYPE OF CONNECTION IS MADE TO GROUND CABLE SHIELDS?
A 360-DEGREE CONNECTION, AVOIDING BREECHES IN THE CONDUCTOR CONTINUITY.
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