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. 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

2. Before a terminal can transmit a message on a multidrop network, what must it first do?

a) Acquire the token
b) Transmit a request to send
c) Wait for the host to send it a poll message
d) None of the above

3. Who or what acts as the controller or "boss" in a multidrop network?

a) The first terminal on the network
b) The system administrator
c) The host computer
d) None of the above

4. Which of these best describes serial data?

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

5. 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

6. 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

7. When we say that a device operates full duplex, what do we mean?

a) It can only communicate in one direction.
b) It can communicate in both directions, but only one at a time.
c) It can communicate in two directions at one time.
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. 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

10. A modulator has an input data rate of 2400 BPS and encodes three bits per transition. Under these conditions, it uses up 1000 Hz of bandwidth. What will happen to the bandwidth if the data rate is reduced to 1200 BPS (and everything else stays the same)?

a) The bandwidth will remain exactly the same
b) The bandwidth will double
c) The bandwidth will become 750 Hz
d) None of the above

11. 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

12. A certain communication system has a bit-cell time of 1 mS and a BAUD of 500. How many bits does it encode per transition?

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

13. 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

14. 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

15. A system transmits data at 19.2 KBPS, and has a signalling rate of 4800 BAUD. How many bits does it encode per transition?

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

16. 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

17. 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

18. Which of these is a method of impressing information onto a carrier wave?

a) Amplitude modulation (AM)
b) Frequency modulation (FM)
c) Phase modulation (PM)
d) All of the above
e) None of the above

19. The rate at which changes are made to an analog carrier wave is called the _______?

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

20. The fundamental units of digital information flow are:

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

21. 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

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

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

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

a) $AB (0xAB)
b) $D3 (0xD3)
c) $D5 (0xD5)
d) None of the above

24. 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

25. When a clock is sent with data, it is called ______ data.

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


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