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Light-Voice Controlling System.

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We are planning to design a new light-voice controlling system. The voices will basically coordinate the crossing of a road by blind people. Suppose the crossing will be operated by two coordinated systems: a light system and a voice system. The light controlling system is an ordinary set of traffic lights intended for vehicles, but with the amber light flashing before the lights change over to green. These lights operate in cycles and display the colors in the order: green, continuous amber, red, flashing amber, green. The set of voices is intended for blind people and makes alternately the voices 'You can cross' and 'Stop'. Making the voice 'You can cross' goes through two phases; a first voice phase 'You can cross' followed by a second voice phase 'Prepare to stop' before the sound change to the 'Stop' voice. The voice 'Stop' lasts through exactly the period from the onset of the green light in traffic lights to the end of the continuous display of the amber light. The periods of playing the voice 'You can cross' and the amber traffic light are also the same. No two lights or two voices are to be displayed or played together at any time in either set when taken in isolation. To simplify the design, we will assume the crossing is not controlled by blind people and that the lights are operated continuously in approximately fixed cycles. Timing parameters of the display of lights or playing of voices are as follows.
Phase Delay of phase
Green light d1
Red light d2
Continuous amber light d3
Flashing amber light d4
Voice 'You can cross' d5
Voice 'Prepare to stop' d6
Voice 'Stop' d7

1) (5 points) Identify all the components of this new crossing system;
2) (15 points) Give a global state transition diagram for this system;

Solution Summary

We are planning to design a new light-voice controlling system. The voices will basically coordinate the crossing of a road by blind people. Suppose the crossing will be operated by two coordinated systems: a light system and a voice system. The light controlling system is an ordinary set of traffic lights intended for vehicles, but with the amber light flashing before the lights change over to green. These lights operate in cycles and display the colors in the order: green, continuous amber, red, flashing amber, green. The set of voices is intended for blind people and makes alternately the voices 'You can cross' and 'Stop'. Making the voice 'You can cross' goes through two phases; a first voice phase 'You can cross' followed by a second voice phase 'Prepare to stop' before the sound change to the 'Stop' voice. The voice 'Stop' lasts through exactly the period from the onset of the green light in traffic lights to the end of the continuous display of the amber light. The periods of playing the voice 'You can cross' and the amber traffic light are also the same. No two lights or two voices are to be displayed or played together at any time in either set when taken in isolation. To simplify the design, we will assume the crossing is not controlled by blind people and that the lights are operated continuously in approximately fixed cycles. Timing parameters of the display of lights or playing of voices are as follows.
Phase Delay of phase
Green light d1
Red light d2
Continuous amber light d3
Flashing amber light d4
Voice 'You can cross' d5
Voice 'Prepare to stop' d6
Voice 'Stop' d7