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| DIGITAL LOGIC EXAMINATION QUESTION - 3 | |
| V. Ryan © 2004 - 2009 | |
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PDF FILE - CLICK HERE FOR PRINTABLE VERSION OF EXERCISE SHOWN BELOW |
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1. A local systems designer has developed a system to control street lights. The street lights can be turned on manually, or by the use of a timer, so long as a light sensing unit indicates that it is dark. |
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1A. Below is an incomplete logic circuit for the control system. Redraw the logic circuit using the correct logic gates. Note the output of the dark/light sensor is 1 (true, high, on) when it is light. The lights must be turned during the dark of night. |
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| 1B. Name the logic gates you have used: | |
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GATE X ................. |
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Below is the logic circuit showing the logic states of inputs and outputs of all the gates when the street lights are ON. |
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Below is the logic circuit showing the logic states of inputs and outputs of all the gates when the street lights are OFF. |
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1C. On the logic
circuit below, write the logic states of all inputs and outputs for the
following: |
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| 1D. Complete the truth table for the logic circuit that controls the street lighting system. | |
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| 1E. Normally a logic circuit such as the one used to control the street lights cannot power lights. In the space below name the subsystem that could be used. | |
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