What is DTMF Decoder , introduction , working of DTMF Decoder , block diagram of DTMF Decoder , components and Implementation of DTMF Decoder Visit my Blog for more Education Material .Thanks http://studyofcs.blogspot.com/search/label/Education

1. National Textile University
Project Proposal
Digital Logic Design
CSC-2072
Title:
DTMF decoder.
Submittedto:
Mr. Nasir Mahmood.
GroupMembers:
Shahmeer Ali (12-NTU-1083)
Mohsin Shoukat (12-NTU-1065)
Ahsan ul Haq (12-NTU-1067)
M. Usman Liaqat (12-NTU-1077)
Introduction:

2. DTMF is a SIPO (Single In Parallel Out) circuit and the abbreviation of Dual-Tone Multi-
Frequency signal which is used by telecommunication companies as a standard to provide
different tasks to their users. Whenever a caller pushes any of the buttons on their keypad a
tone of a unique frequency will be generator with the DTMF generator and sent to the receiver.
The receiver receives the frequency and decodes it using DTMF decoder. So DTMF decoder is a
circuit that decodes the signals generator at the caller side.
This projectconsists of a DTMF decoder as a core of this project which will be connected to the
microphone of a cellphone at receiver side. The cellphone will be in an auto answer mode, so
when the caller calls the receiver the call will be auto-received and when the caller presses
desired button the generated DTMF code will be send to receiver cellphone and decoded using
the DTMF decoder and the 4-bitbinary fromthedecoder will then performdifferenttasks using
relays.
Working:
When the cellphone auto-receives the call, the electric signals will be transferred to the
input signal of DTMF decoder using microphone jack. The frequency of the signals will be the
superposition of two frequencies as shown in the fig.
DTMF decoder decodes the signals and generates a binary code of the key pressed by the caller
as shown in the fig.

3. The output will be a parallel output so simple AND and NOT gate circuits will be used to make
the decisions and switches the replays. Relays will be attached with the circuit that will be
decided by the binary bits of output.
Basic BlockDiagram:
Components needed:
 Power supply of 9 volts.
 Cellphone with an auto-answering function.
 Microphone jack.
 DTMF Decoder (MT-8870 OR HT-9170) based on the availability.
 AND gate and NOT gate ICs.
 Clock generator of (3.579545 MHz) {Oscillator}.
 Relay switches.
 A 4 to 16 De-Multiplexer.

4. Implementation:
This basic DTMFdecoder circuit can bemodified accordingto the desiredimplementation
and can be used to:
 Turn the electronic devices at home on/off while away.
 Lock/unlock the door with a mechanical modification.
 To access and execute commands on a computer using a specialized software.