1. by by  Y.MADHU KEERTHANA (084A1A0459)  RAHIM BASHA (084A1A0441)  G.BABJI REDDY (084A1A0416)  V.REVATHI (084A1A0456 ) UNDER THE GUIDENCE OF….... Mr.T.E.ARAVINDAN, M.TECH 1-6-2011 1

2. DTMF is the replacement of old rotary dial telephone and DTMF stands for Dual Tone Multiple Frequency. When a number is dialed on DTMF keypad corresponding higher and lower frequencies merge and a dial tone is generated.. The dial tone generated is decoded in the exchange office. When decoding is done, code generated can be identified. ABSTRACT 1-6-2011 2

3. DTMF keypad frequencies (with sound clips) 1209 Hz1336 Hz1477 Hz1633 Hz 697 Hz 123A 770 Hz 456B 852 Hz 789C 941 Hz *0#D 1-6-2011 3

4. For example, if the key '1' is being press on the phone, the tone you hear is actually consist of a 697hz & 1209hz sine signal. Pressing key '9' will generate the tone form by 852hz & 1477hz. The frequency use in the dial tone system is of audible range suitable for transmission over the telephone cable. 1-6-20114

5. INTRODUCTION This project describes the controlling of a system by interfacing the telephone line. Using this interface any device can be controlled using a telephone or cell phone. The system involves the use of DTMF tones commonly used in telephone networks. 123A 697 Hz 456B 770 Hz 789C 852 Hz *0#D 941 Hz 1209 Hz1336 Hz1477 Hz1633 Hz 1-6-2011 5

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7.  It uses DTMF encoder integrated circuit, Chip UM 91214 B.  This IC produces DTMF signals. It contains four row frequencies and three column frequencies.  The pins of IC 91214 B from 12 to 14 produces high frequency column group and pins from 15 to 18 produces the low frequency row group.  By pressing any key in the keyboard corresponding DTMF signal is available in its output pin at pin no. 7. 1-6-2011 7

8. DECODER 8

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10. DT MF SIGNALLING WORKS ON VIRTULLY ALL RADIO SYSTEMS OPTIONAL TELECO INTERFACE COST EFFECTIVE 1-6-2011 10

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12. APPLICATIONS Control the light of advertising board: Credit card system In remote control systems In personal computers Telephone answering machine PBEX 1-6-2011 12

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