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Alford, R. and Pryor, N. (1992). Learning needs in industry: Meeting the challenge. In J. G. Hedberg and J. Steele (eds), Educational Technology for the Clever Country: Selected papers from EdTech'92, 39-48. Canberra: AJET Publications. http://www.aset.org.au/confs/edtech92/alford.html
Date: 03 Aug 1992 QEC ELMS (C) Page 1
Time: 09:17:05 Learning Unit 92 Test : Attempt 1 User: gb101
L.PGRM: PROT_1
Learning Unit INTRODUCTION TO POWER LINE CARRIER
Question 1. ( 4) (92/0l/007)
----------------------------
In PLC channels it is common practice to reduce the usable upper range
from 3.4 kHz to 2.4 kHz. This done:
(l) to achieve better speech quality
(2) to reduce the overall noise in the channel
(3) to allow data channels more chance of working when noise levels rise
(4) to allow more signalling information down the channel
Enter your answer 1-4 [ ]
=====================================
Question 2: ( 10) (92/01/008)
-----------------------------
Some power supply authorities purchase PLC line traps to cover the range
150 to 480 kHz with a minimum of 1000 ohms impedance. Using the appropriate
formula, how much inductance would this line trap have RELATIVE to one of
similar construction but with a frequency range of 120 to 300 kHz and a
minimum impedance over this range of 600 ohms.
Enter your answer to two decimal places [ ]
Question 3 ( 10) (92/02/001)
----------------------------
Consider the Figure in Appendix C of Module 601 which shows the frequency
response of a 'High Band' line trap. The original specification required
l000 ohms blocking impedance from 300 to 480 kHz. In fact, from the curve
supplied, this blocking impedance is achieved (enter your answer in kHz):
from a low frequency of [ ]
to a high frequency of [ ]
This extension of the frequency range beyond that specified would allow
the end user:
to install more PLC channels for speech circuits Y or N [ ]
to install more. PLC channels for data circuits Y or N [ ]
to install more. PLC channels for proc. sig circuits Y or N [ ]
=====================================
***** End *****End
L.PGRM: PROT_1
Learning Unit INTRODUCTION TO POWER LINE CARRIER
Question 1. ( 4) (92/0l/007)
1 Incorrect - Correct Answer is 4
Ans 1. The restriction lowers speech quality in fact.
Ans 2. The overall channe1 bandwidth has not been changed
(300-3900 Hz, eq.). Therefore noise into the overall
channel is not affected.
Ans 3. Any individual data channel (eg, 48O Hz wide) will have its own
filters which will restrict the noise. This noise is then
independent of PLC channel width.
Ans 4. As simple as that.
Marks 0.0 out of 4.0
Question 2 ( 10) (92/01/008)
1.23 Incorrect - Correct Answer is 1.53
K 7000 (480-150)
Inductance, 150 to 480 kHz = --------------- = 4.5833 K
480 x 150
K 600 (300-120)
Indutance, 120 to 300 kHz = ---------------- = 3.0000 K
300 x 120
RATIO = 1.53
Marks 0.0 out of 10.0
Question 3. ( 10) 192/02/001)
250 Correct
550 Incorrect - Correct Answer is 500
y Incorrect - Correct Answer is N
y Incorrect - Correct Answer is N
y Correct
The program is set to accept 250+-10 and 500+-10 kHz for the low to high
frequency range.
The frequency extension above 480 kHz is not useful because allocations here
are not allowed. Frequency extension below 300 kHz is still in the
"normally quiescent" zone, and can only be used for "normally quiescent"
protection signalling. Since 300 - 380 kHz is already available for this,
the extension to 250 kHz would not represent much practical gain.
Marks 4.0 out of 10.0