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# (Solved): 4.4 Telephone Numbers The functions $$d t m f d i a l . m$$ and $$d t m f ... ??????? 4.4 Telephone Numbers The functions \( d t m f d i a l . m$$ and $$d t m f r u n . m$$ can be used to test the entire DTMF system as shown in Fig. 8. You could also use random digits (e.g., ceil $$(15.9 *$$ rand $$(1,22)+0.09))$$ in place of $$1: 16$$ in dtmfdial. For the dtmfrun function to work correctly, all the M-files must be on the MatLAB path. It $$\gg>\mathrm{f}=8000 ;$$ ?<-use this sampling rate in all functions $$\gg t k=\left[A^{\prime}, B^{\prime},{ }^{\prime} C^{\prime}, D^{\prime}, D^{\prime} *^{\prime},^{\prime} \#^{\prime}, \prime^{\prime}, \prime^{\prime} 1^{\prime}, 2^{\prime}, \prime^{\prime} 3^{\prime},{ }^{\prime} 4^{\prime},{ }^{\prime} 5^{\prime}, 6^{\prime} 6^{\prime}, 7^{\prime} 7^{\prime}, 8^{\prime}, 9^{\prime}\right]$$; $$\gg \mathrm{xx}=\mathrm{dtmfdial}(\mathrm{tk}$$, fs ); >soundsc (xx, fs) $$>$$ > $$=\ldots$$ ?<-use your value of $$\mathrm{L}$$ $$\gg$$ dtmfrun (xx, L, fs) ans $$=$$ $$A_{A B C}{ }^{*} \# 0123456789$$ Figure 8: Testing the DTMF system. is also essential to have short pauses in between the tone pairs so that $$d t m f c u t$$ can parse out the individual signal segments. If you are presenting this project in a lab report, demonstrate a working version of your programs by running it on the following phone number: $407 * 89132 \text { \#BADC }$ In addition, make a spectrogram of the signal from $$\mathrm{dtmfdial}$$ to illustrate the presence of the dual tones.

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