ET270 Practice Test I

Instructions: There are 25 questions on this test. It is written in a style very similar to the REAL exam #1. Choose the best answer from among those given. Click the GRADE button on the bottom of the form when you want the exam graded.

Note: You can practice this test as many times as you desire; the system will cook you up a fresh batch of questions each time you access this page.

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1. What is the primary disadvantage of a point-to-point (peer-to-peer) network?

a) Complicated protocol is required.
b) The security of such a network is very poor.
c) Possible high cost per unit, due to low communications line utilization.
d) None of the above

2. Parallel data is best described as:

a) All bits are sent at the same time.
b) One bit is sent at a time.
c) The data represented in analog form.
d) None of the above

3. When a host wants to check to see if a terminal (slave) unit on a multidrop network has anything to say, what does it do to the terminal?

a) It stops all processing and waits for the terminal to send a message.
b) It transmits a poll message with the terminal's address.
c) It continues processing; the terminal will interrupt it when ready.
d) None of the above

4. When all data bits are sent at the same time, we are sending what type of data?

a) Digital
b) Serial
c) Parallel
d) None of the above

5. What is one disadvantage of serial data over parallel data?

a) The hardware to generate serial data is very expensive.
b) Serial data is much more prone to transmission errors than parallel.
c) The transmission speed of serial data is slower.
d) None of these

6. Which of these is best described by the term demodulation?

a) Analog to digital conversion in a modem receiver
b) Digital-to-analog conversion in a modem
c) Converting parallel data to serial data
d) None of the above

7. A ______ system can only communicate in one direction. (Fill in the blank.)

a) Simplex
b) Half-duplex
c) Full-duplex
d) None of the above

8. What two factors determine the information carrying capacity of a communications channel?

a) Bandwidth and power gain
b) S/N ratio and bandwidth
c) Power gain and S/N ratio
d) None of the above

9. Which of the below factors limits the number of bits per transition in practical communication systems?

a) Channel power gain
b) Channel bandwidth
c) Channel S/N ratio
d) None of the above

10. In FSK, what property of the carrier is changed in order to represent the data?

a) Amplitude
b) Phase
c) Frequency
d) None of these

11. The fundamental units of digital information flow are:

a) BAUD
b) CPS
c) BPS
d) None of the above

12. Which modulation method below changes the frequency of the carrier in order to represent the data?

a) FSK
b) ASK
c) PSK
d) None of these

13. What type(s) of modulation are occuring in the figure above?

a) AM
b) FM
c) PM
d) Both A and C
e) None of the above

14. In a single-level modulation system, how many bits are represented for each transition?

a) 2
b) 3
c) 4
d) None of the above

15. How many bits are encoded per transition in the figure above?

a) 1
b) 2
c) 3
d) None of the above

16. The data rate into a modulator is 1200 BPS, and its constellation is shown above. What will the signalling rate be?

a) 600 BAUD
b) 300 BAUD
c) 150 BAUD
d) None of these

17. What is a primary fault of single-level modulation systems?

a) They are slow and don't use bandwidth efficiently
b) They use excessive bandwidth
c) They are very sensitive to noise
d) None of the above

18. If a certain modulator produces a change in the carrier every 1 mS, what is the resulting signalling rate?

a) 500 BAUD
b) 1000 BAUD
c) 2000 BAUD
d) None of the above

19. What is meant by the terms "mark" and "space?"

a) Off and On conditions
b) Logic 1 and Logic 0 conditions
c) Ready or Not Ready conditions
d) None of these

20. A certain system has 16 modulation states and has a signalling rate of 600 BAUD. What will the resulting data rate be?

a) 1200 BPS
b) 2400 BPS
c) 4800 BPS
d) None of the above

21. In the figure above, the parameters are 8,N,1 and the bit time is 1 mS. How many characters can be sent per second?

a) 125
b) 111
c) 100
d) None of the above

22. Given that the parameters are 8,N,1 above, what hex data value is being sent?

a) $F3 (0xF3)
b) $A5 (0xA5)
c) $AF (0xAF)
d) None of the above

23. In the figure above, the parameters are 8,N,2 and the bit time is 500 uS. How many characters can be sent per second?

a) 125
b) 136
c) 181.8
d) None of the above

24. What type of data is sent without a clock signal?

a) Asynchronous
b) Synchronous
c) Analog
d) None of the above

25. In the above figure, 8 data bits, 1 stop bit, and a parity bit are being sent. What type of parity is in use?

a) Odd
b) Even
c) Can't tell from information given


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