Topic 1, Principles of Transmission

Question 1

If the input signal power to a communication system is 1 W and the output power is 1 mW, the system attenuation is:

A. 3 dB
B. 20 dB
C. 30 dB
D. 40 dB
E. 1000 dB

Answer 1

C. 30db

Question 2

The signal at the input to a balanced twisted pair cable is 10 mW. The cable is 1000 feet long and has an attenuation of 1 dB per 100 feet. This cable is connected to the input of a receiver. The noise level at the input to the receiver is 1 microwatt. What is the signal-to- noise ratio (SNR) (dB) at the receiver input?

A. 10 dB
B. 30 dB
C. 40 dB
D. 60 dB
E. 100 dB

Answer 2

B. 30db

Question 3

A SONET OC-1 channel can carry 672 voice signals and has a data rate of 51.84 Mbps. A
SONET OC-48 channel can carry 32,256 voice channels. What MINIMUM data rate is required for the OC-48 channel?

A. 155 Mbps
B. 622 Mbps
C. 2.5 Gbps
D. 5 Gbps
E. 10 Gbps

Answer 3

C. 2.5gbps

Question 4

All of the following are nominal wavelengths for laser light sources EXCEPT:

A. 700 nm
B. 850 nm
C. 1300 nm
D. 1310 nm
E. 1550 nm

Answer 4

A. 700nm

Question 5

A video camera has a coaxial cable output. The video signal is to be distributed to devices that have balanced twisted pair inputs. The transition between these two different transmission media can be accomplished by using a:

A. Balun
B. Converter
C. Modulator
D. Cross connect
E. Transceiver

Answer 5

A. Balun

Question 6

The public telephone system is an example of a __________ system.

A. Simplex
B. Half-duplex
C. Full-duplex
D. Purely analog
E. Purely digital

Answer 6

C. Full-Duplex

Question 7

Wave division multiplexing (WDM) is most similar to:

A. Amplitude modulation
B. Frequency modulation
C. Time division multiplexing
D. Frequency division multiplexing
E. Carrier sense multiple access with collision detection (CSMA/CD)

Answer 7

D. Frequency division multiplexing

Question 8

You must place CAT6 cable above a factory floor with automated welding machines and hammer forges. Of the following, what type of shielding would be most effective?

A. Multi-layer braid
B. Foil and braid
C. Solid metallic conduit
D. Flex metallic conduit
E. Sch. 40 PVC conduit

Answer 8

C. Solid metallic conduit

Question 9

You must place a cable between 2 equipment locations with separate grounds having a potential difference between them of 2.1 V rms. Which one of the following cables should
NOT be used?

A. Multimode
B. Singlemode
C. UTP
D. STP

Answer 9

D. STP

Question 10

Two sinusoidal signals have the same amplitude (A) and the same frequency (f). They differ in phase by 180 degrees. If these two signals are added together, the result is a sinusoidal signal having an amplitude of:

A. Zero
B. 0.707A and a frequency of f
C. A and a frequency of 2f
D. 2A and a frequency of f
E. 2A and a frequency of 2f

Answer 10

A. Zero

Question 11

Composite conductors, although not generally recommended, may be used in special circumstances because they provide all of the following advantages EXCEPT:

A. Have good digital transmission characteristics
B. Lightweight
C. Inexpensive
D. Easy to produce
E. Easily embedded into other materials

Answer 11

A. Have good digital transmission characteristics

Question 12

Which is an advantage of stranded conductors over solid conductors?

A. Less costly
B. Simpler terminations
C. Better high frequency performance
D. More flexible

Answer 12

D. More flexible

Question 13

The conversion of an analog speech signal to a pulse code modulation (PCM) digital signal involves all of the following steps EXCEPT:

A. Low pass filtering
B. Periodic sampling
C. Quantizing
D. Companding
E. Amplitude modulation

Answer 13

E. Amplitude modulation

Question 14

Assume that the optical power transmitted by a 62.5/125 multimode fiber is distributed uniformly across its core. If this fiber is perfectly coupled (i.e., the two fibers are aligned and abutted) to a 50/125 fiber, what is the percent of power that is lost?

A. 0 percent
B. 36 percent
C. 50 percent
D. 80 percent
E. 100 percent

Answer 14

B. 36%

Question 15

Which of the following correctly lists the lowest frequency band to the highest frequency band?

A. MF, HF, VHF, UHF
B. UHF, VHF, HF, MF
C. HF, MF, UHF, VHF
D. VHF, UHF, MF, HF
E. HF, MF, UHF, VHF

Answer 15

A. MF, HF, VHF, UHF

Question 16

Time division multiplexing (TDM) systems are designed to transport ________ between end point systems.

A. Only analog signals
B. Only digital signals
C. A mix of both analog and digital signals
D. Both analog and digital signals, but only one type at a time

Answer 16

B. Only digital signals

Question 17

A reasonable approximation for the signal speed in 100 ohm balanced twisted pair cable is
__________, where c is the velocity of light in free space.

A. 0.2 c
B. 0.4 c
C. 0.6 c
D. 08 c
E. 0.9 c

Answer 17

C. 0.6 c

Question 18

Which characteristic is an advantage of copper based media over optical fiber cable?

A. Weight
B. Corrosion resistance
C. Ability to handle analog signals
D. Susceptibility to EMI
E. Very high data rates

Answer 18

C. Ability to handle analog signals

Question 19

Which electrical characteristic is displayed with the correct preferred value?

A. Dielectric constant – high value
B. Dielectric strength – high value
C. Dissipation factor – low value
D. Insulation resistance - high value

Answer 19

A. Dielectric constant - high value

Question 20

Optical transmitters are typically one of the following types EXCEPT:
A. Light-emitting diode (LED)
B. Short wavelength laser compact disc (CD)
C. Vertical cavity surface emitting laser (VCEL)
D. Laser diode (LD)
E. Overfilled launch (OFL)

Answer 20

E. Overfilled launch (OFL)