Tuesday, October 14, 2008

ECE Board Exam.Review 1996

1. That dielectric material of an optical fiber surrounding the core
(A) Cladding
B. Armor
C. Shield
D. Cover
2. An antenna that is circularly polarized is the ______.
A. parabolic reflector
(B) helical
C. Yagi-uda
D. small circular loop
3. A word in telegraphy consist of _____ Characters plus a word space
A. 11
(B) 7 and ½
C. 8
D. 5
4. The number of voice band channels in a master group per CCITT standard is ______.
(A) 300
B. 480
C. 600
D. 120
5. The power of standard test tone is normally ______.
A. 1 dB
B. 0 mW
(C) 1 mW
D. 1 W
6. LORAN is a navigation system used primarily for
A. approach control
(B) obtaining fixes over large distances
C. blind landing
D. automatic collision warning
7. At what power level does a 1kHz tone cause zero interference (144 weighted)?
A. -90 dB
(B) -90 dBm
C. 90 dBm
D. 90 dB
8. One character or a sequence of characters forming a part, or the whole of a message with a specific meaning.
A. Signs
B. Call sign
(C) Code
D. Identifier
9. The K-factor under normal atmospheric conditions in a microwave radio data profile calculation is equal to ______.
A. 2/3
B. 0
(C) 4/3
D. infinity
10. What is the IBM’s asynchronous data link protocol designation?
(A) 83 B
B. 8A1/8B1
C. 93 B
D. 9 A1/9B1
11. EIRP stands for _______.
A. effective isotropic refracted power
B. efficient and ideal radiated power
C. effective isotropic reflected power
(D) effective isotropic radiated power
12. The modulation system used for telegraphy is
(A). frequency-shift keying
B. two-tone modulation
C. pulse-code modulation
D. single-tone modulation
13. The standard that specifies a balanced interface cable that will operate bit rates up to 10 Mbps with a span distances up to 1200 m.
(A) RS-423A
B. RS-422A
C. RS-550A
D> RS-449A
14. The antenna which is not resonant at s particular frequencies and so can be used over a wide band of frequencies is called
(A) aperiodic
B. boresight
C. cassegrain
D. top-loaded
15. ______ occurs when the microwave beam is at point of grazing over an obstacle.
(A) Diffraction
B. Refraction
C. Absorption
D. Reflection
16. Atmospheric condition is controlled by
A. humidity
B. pressure
C. temperature
(D) all of these
17. The characteristic impedance of a transmission line does not depend uponits ____.
A. conductor spacing
B. conductor diameter
(C) length
D. conductor radius
18. The point on the satellite orbit, closest to the earth is
A. progade
(B) perigee
C. zenith
D. apogee
19. The potential difference between any exposed structured to ground in any electrical installation should not exceed ______ volts RMS.
A. 10
(B) 45
C. 0
D. 30
20. The capture area of an antenna is directly proportional to the
A. frequency of the received signal
B. distance between transmitter and receiver
(C) gain of antenna
D. power density of the signal
21. Modems are required to connect computer to telephone lines because _______.
A. telephone company rules required them
B the telephone network bandwidth is too high
C. none of the above
(D) the telephone network will pass direct current
22. The standard reference antenna for the directive gain is ________.
A. elementary doublet
(B) isotrophic antenna
C. half-wave dipole
D. infinitesimal dipole
23. It is a spacecraft placed in orbit around the earth carrying onboard microwave
receiving and transmitting equipments.
A. Fiber optic equipment
(B) Communications satellite
C. Wireless radio system
D. Coaxial cable system
24. One type of pulse communications system uses pulse that appear as a group,
and which vary in number according to the loudness of the voice. This type of
Pulse modulation is called
(A) pulse duration modulation
B. pulse amplitude modulation
C. pulse code modulation
D. pulse position modulation
25. A device to be connected across the headset in telephone receivers to reduce
the effects of acoustic shock.
A. Ground
(B) Two rectifiers in parallel with opposite polarities
C. Protector
D. Fuse
26. Judgment on the case against an ECE shall become final and executory after
A. 10 days
B. 60 days
(C) 30 days
D. 15 days
27. The equivalent noise temperature of the amplifier is 25 K. What is the noise
figure?
A. 1.86
B. 0.1086
(C) 1.086
D. 10.86
28. The letter-number designation B8E is a form of modulation also known as
_________.
A. pilot-carrier system
(B) independent sideband emission
C. lincomplex
D. vestigial sideband transmission
29. When the transmission and receiving antennas are in line-of-sight of each other,
the mode of propagation is _________ wave.
(A) space or direct
B. ground
C. surface
D. sky
30. According to the Nyquist theorem, the sampling rate that can be used in a PCM
system is _______ the highest audio frequency.
A. once
B. eight times
(C) twice
D. thrice
31. Passive crossover components cause some frequencies to be delayed with
respect to the other frequencies at the crossover point.
(A) Phase shift
B. Phase correction
C. Phase-error correction
D. Time alignment
32. A car horn outdoors produces a sound intensity level of 90 dB at 10 ft away. At
this distance, what is the sound power in watt?
A. 12 W
(B) 0.12 W
C. 0.012 W
D. 1.2 W
33. What is one principal difference between synchronous and asynchronous
transmission?
A. the pulse height are different
( B) the clocking is derived from the data in synchronous transmission
C. the clocking is mixed with the data in asynchronous
D. the bandwidth required is different
34. The lowest layer is the ionosphere.
(A) D
B. F2
C. E
D. F1
35. What is the number of pins in the RS-232C interface?
(A) 25
B. 15
C. 20
D. 20
36. SSB transmission requires only _______ of the bandwidth for a DSBFC
transmission.
A. ¼
B. 2/3
(C) ½
D. ¾
37. The method of generating FM used by broadcasting station i
A. direct
B. all of these
(C) indirect
D. insertion
38. What is the transmission rate of a system for transmitting the output of a
microcomputer to a line printer operating at a speed of 30 lines/minute?
assume that the line printer has 8 bits of data per character and prints out 80
characters/line.
A. 800 bps
B. 400 bps
(C) 320 bps
D. 640 bps
39. Communications code is _________.
A. eight bits per character
(B) agreed upon in advance between sender and receiver
C. the same in all modern computers
D. either seven or eight bits per character
40. What is the reference tone level for dBm?
A. -82 dBm
B. -85 dBm
C. -67 dBm
(D) -90 dBm
41. A type of an undergrounded antenna is a/an _________ antenna.
(A) Hertz
B. isotropic
C. parabolic
D. Marconi
42. Which of the following pulse modulation systems is analog?
A. Delta
B. Differential PCM
(C) PWM
D. PCM
43. TACAN is a navigational aid providing _________.
(A) bearing and distance indication
B. speed and height indication
C. bearing and weather information
D. instrument-landing glide paths
44. In ________ transmission, a unique SYN character is transmitted at the
beginning of each message.
A. asynchronous
(B) synchronous
C. digital
D. analogue
45. If the terminating impedance is exactly equal to the characteristic impedance of
the transmission line the return loss is _______.
A. zero
B. one
(C) infinite
D. none of these
46 What is the main purpose of a communication systems?
A. None of these
B. To have a frequency assignment
C. For modulation
(D) To provide an acceptable replica of the information at the destination.
47. In the phase shift method, how many circuits must be balanced?
A. none of these
(B) 1
C. 4
D. 2
48. The carrier swing necessary to provide 80% modulation in the FM broadcasting
band is ________.
A. 150 kHz
B. 120 kHz
C. 60 kHz
(D) 75 kHz
49. The correctness and accuracy of the transmitted message content is
A. verified by the modem
(B) communication system
C. determined by the sender and receiver
D. ensured by use of digital technique
50. After the IF stages have been aligned, the next stage to align in FM receiver is
(A) local oscillator
B. limiter stage
C. RF amplifier
D. mixer stage

1 comment:

Unknown said...

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