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DISPLAY OF DIALED TELEPHONE NUMBERS ON SEVEN

SEGMENT DISPLAYS

ABSTRACT

The main objective of this project is to display the dialed telephone number on seven

segment display for better visibility. This project is based on the concept of DTMF (dual tone

multi frequency). Every button on the ey pad of a telephone generates a unique frequency !hen

pressed. These frequencies are decoded by a DTMF decoder and the digital signals are fed to the

microcontroller through buffer circuits. "hile the program is e#ecuted$ the output of the

microcontroller delivers the same data to parallel connected seven segment displays.

The parallel connected seven segment displays operate in the multiple#ing mode fed from

the microcontroller through driving s!itches to generate e#act display of the numbers dialed. %n

actual operation only one seven segment display sho!s the number at any given time out of the

ten used. &!ing to persistence of vision$ all the numbers appear glo!ing at the same time as they

are in high speed multiple#ing mode. The project uses an '* family microcontroller$ and a cell

phone duly connected from its ear phone socet to the DTMF decoder for receiving the data.

This data is transmitted to the microcontroller for processing. The processed data is then given to

the parallel connected seven segment displays.

Further the project can be enhanced to displaying the time$ cost$ day and date parameters

on the digital display.

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