On a Touch-Tone phone, each button produces a unique
Chapter 7, Problem 47(choose chapter or problem)
On a Touch-Tone phone, each button produces a unique sound. The sound produced is the sum of two tones, given by y = sin12plt2 and y = sin12pht2 where l and h are the low and high frequencies (cycles per second) shown on the illustration. For example, if you touch 1, the low frequency is l = 697 cycles per second and the high frequency is h = 1209 cycles per second. The sound emitted by touching 1 is
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