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

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

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

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

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

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 It uses DTMF encoder integrated circuit, Chip UM B.  This IC produces DTMF signals. It contains four row frequencies and three column frequencies.  The pins of IC 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

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DT MF SIGNALLING WORKS ON VIRTULLY ALL RADIO SYSTEMS OPTIONAL TELECO INTERFACE COST EFFECTIVE

APPLICATIONS Control the light of advertising board: Credit card system In remote control systems In personal computers Telephone answering machine PBEX