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 key pad of a telephone generates a
unique frequency when pressed. These frequencies are decoded by a DTMF decoder
and the digital signals are fed to the microcontroller through buffer circuits.
While the program is executed, the output of the microcontroller
delivers the same data to parallel connected seven segment displays.
The parallel connected
seven segment displays operate in the multiplexing mode fed from the
microcontroller through driving switches to generate exact display of the
numbers dialed. In actual operation only one seven segment display shows the
number at any given time out of the ten used. Owing to persistence of vision,
all the numbers appear glowing at the same time as they are in high speed multiplexing
mode. The project uses an 8051 family microcontroller, and a cell phone duly
connected from its ear phone socket 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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