I am in my first year at university and I have been given the following assignment:

Implement a support system for the safety of passengers inside motor vehicles.

The system must ensure that the vehicle's ignition is only activated if some conditions of safety, that is, if driver and passenger have their safety belts fastened. If the safety conditions are not met, the system should display a warning light when the vehicle is on (K activated). If the warning signal is active, the system must prevent ignition (S activated).

The system has the following input signals:

  • (CC) Driver Belt Sensor;
  • (CA) Companion Belt Sensor;
  • (A) Companion presence sensor;
  • (K) Vehicle key to establish general power;
  • (S) Momentary Start activation to promote ignition.


Get the simplified expressions of the Alert and Ignition outputs.

I tried to assemble the truth table but I can't find out what is the parameter of the operations to follow for the alarm (the values ​​of alert) or each possibility.

Here's the example of a similar problem's solution down below:

Assume that you get the following expressions: π΄π‘™π‘’π‘Ÿπ‘‘π‘Ž = ~𝐴. 𝐢𝐴 + ~𝐢𝐢 and πΌπ‘”π‘›π‘–Γ§Γ£π‘œ = ~π΄π‘™π‘’π‘Ÿπ‘‘π‘Ž + ~𝑆. So the door logic to use are: AND, OR and NOT.

I apologise if there are errors in my explanation, we've only done the truth table with the non-simplified expression (I know how to get the simplified expression through the V-K maps but I can't get my head around the results or alarm based on the inputs.

Can you help me solve this problem?

  • 2
    \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Nov 6, 2021 at 12:07
  • \$\begingroup\$ step1: make a table of every possible permutation of input. step2: add output columns and fill in the logic according to the statements. \$\endgroup\$
    – Abel
    Nov 6, 2021 at 12:30
  • 1
    \$\begingroup\$ Since this is a homework problem we will expect you to show us that you have made a substantial effort to solve this yourself. Show us all of your work, then ask a specific question. \$\endgroup\$ Nov 6, 2021 at 12:36
  • \$\begingroup\$ @Abel my problem is in the fill in the logi acording to the statement part, usually I would get an expression like F=A*B then would use it to get the output 1 or 0 in each permutation of output but I dont hae nothing like it in the result. \$\endgroup\$ Nov 6, 2021 at 12:37
  • \$\begingroup\$ What inputs do you have? What outputs do you have? Draw a table with columns for the inputs and columns for the outputs. Use the description from the assignment to fill the truth table. From the truth table, you can derive an expression, and from that the circuit. \$\endgroup\$
    – JRE
    Nov 6, 2021 at 12:52

1 Answer 1


Rather than solve your homework, I'll present a different problem. I believe this is a lesson in turning the somewhat inconsistent and often illogical source of information that is language into a slightly more logical form that is a truth table.

The light shall turn on when the light switch is in the on position. The light cannot turn on if there is a power outage.


A. The light switch is in the on position.

B. There is a power outage.

Output: The light is on

Step 1 would produce:

The light switch is in the on position There is a power outage The light is on
T T ?
T F ?
F T ?
F F ?

What would the Output column be per step2, your understanding of lights, and power outages?

What if we add another input of the form:

A functioning backup generator can compensate for a power outage.

Input: The backup generator is functional.

  • \$\begingroup\$ Thank YOU !! I managed to solve the problem using your example. \$\endgroup\$ Nov 6, 2021 at 21:50

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