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Projects DetailsDTMF based mini projects
Jan 01, 2013 Posted by Abhi Raj
This telephone-operated calling circuit is very helpful for doctors in calling the patients, in banks and in various other situations where persons have to be called or signalled. When you need to call a person amongst many standing outside your cabin, just lift the telephone handset off the cradle and press the respective number. The number of the person called will be displayed and a bell will sound to inform the person that it is his turn.
Dual-tone multiple-frequency (DTMF) receiver IC is commonly used in telephone equipment. One common DTMF receiver is Holtek HT9170 used in electronic communication circuits. The Holtek HT9170 series comprises DTMF receivers integrated with digital decoder and bandsplit filter functions. All HT9170 series ICs use digital counting techniques to detect and decode all the 16 DTMF tone pairs into a 4-bit code output.The circuit can also be used in quiz contests and by visually- or hearingimpaired people. It can be used to call a maximum of nine different persons. The circuit is built around DTMF receiver IC HT9170, BCD-to-7-segment decoder/driver 7447, quad 2-input OR gate and common-anode display. Simple melody generator IC UM66 is used to produce melody sound in the loudspeaker through Darlington-pair transistors (T1 and T2).The tone pair DTMF generated by pressing the telephone key is converted into binary values internally in the IC. The binary values are indicated by the glowing of LEDs at the output of IC1.
This telephone-operated calling circuit is very helpful for doctors in calling the patients, in banks and in various other situations where persons have to be called or signalled. When you need to call a person amongst many standing outside your cabin, just lift the telephone handset off the cradle and press the respective number. The number of the person called will be displayed and a bell will sound to inform the person that it is his turn.
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Dual-tone multiple-frequency (DTMF) receiver IC is commonly used in telephone equipment. One common DTMF receiver is Holtek HT9170 used in electronic communication circuits. The Holtek HT9170 series comprises DTMF receivers integrated with digital decoder and bandsplit filter functions. All HT9170 series ICs use digital counting techniques to detect and decode all the 16 DTMF tone pairs into a 4-bit code output.The circuit can also be used in quiz contests and by visually- or hearingimpaired people. It can be used to call a maximum of nine different persons. The circuit is built around DTMF receiver IC HT9170, BCD-to-7-segment decoder/driver 7447, quad 2-input OR gate and common-anode display. Simple melody generator IC UM66 is used to produce melody sound in the loudspeaker through Darlington-pair transistors (T1 and T2).The tone pair DTMF generated by pressing the telephone key is converted into binary values internally in the IC. The binary values are indicated by the glowing of LEDs at the output of IC1.
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