Exercise DET-02.02 – Smartphone display on

Prof. Dr. Thorsten Jungmann (last updated 2026-10-12)

Relates to DET-02 Logic operations

Task

Many smartphones switch their screen on when you press the power button ($A$), when you lift the phone ($B$) or when a notification arrives ($C$); one of the three is enough. The output is $Y$, ‘screen on’. Subtask a) is based on an exercise in the textbook by LaMeres [5, p. 84].

a) Set up the truth table of $Y$.

b) Draw the Karnaugh map of $Y$.

c) Draw the schematic symbol of the gate that forms $Y$, according to the standard of the International Electrotechnical Commission (IEC), IEC 60617.

Solution

a) $Y=A+B+C$; $Y$ is 0 only in row 0, where all three inputs are 0
b) a single 0, at the top left in the cell of row 0, where all three inputs are 0; a 1 in each of the other seven cells
c) a rectangle with the qualifying symbol ≥1, with the three inputs $A$, $B$ and $C$ and the output $Y$

▶️ Full worked solution