DTM Decoder
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The document is a project proposal for a DTMF decoder, submitted to Mr. Nasir Mahmood by a group of students. It explains the functioning of DTMF technology, which allows signals generated by a caller's keypad to be decoded into binary codes that can control various devices. The project aims to create a circuit that connects to a cellphone in auto-answer mode, enabling remote control of electronic devices through DTMF signals.
DTM Decoder
- 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.