DTMF Tele controller

Discussion in 'General Electronics Chat' started by hsu, Feb 5, 2010.

  1. hsu

    Thread Starter New Member

    Feb 5, 2010
    1
    0
    Can anybody give me the schematic and details of DTMF land-line remote Tele controller, which not using any micro controller????
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,576
    231
    Check the February 2010 issue of Nuts and Volts Magazine..."TouchTone Phone Controller".
    Uses a dedicated HT9107B DTMF decoder and CMOS logic, but not a programmable μcontroller.

    Ken
     
  3. vinodquilon

    Member

    Dec 24, 2009
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    Dear Ken,
    It is first time I heard about Nuts and Volts. I am from India, there Electronics For You magazine is more popular. It is very interesting and helpful to read Nuts and Volts and gave lot of improvements to my touch-tone project.
    Thanks for all helps...
     
  4. vinodquilon

    Member

    Dec 24, 2009
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    I have read the article and have the following suggestions,

    1. 4514 decoder inhibits its outputs to all zeros when INHIBIT pin goes HIGH, but the author wrote "whatever position you left it in after you pressed the hash key will remain until it's changed by you".

    2. 4514 decoder latches hold the last in data prior to strobe one to zero transition, but according to the author on pressing the asterisk key the decoder strobe input goes high to low and remain in low for 150ms. Only after this one to zero transition we enter decimal key press to latch.


    These two drawbacks can be easily rectified using latched D Flip Flop (remain output device in previous state, to change state once again the same key press needed) at outputs and MT8870 DTMF decoder (itself contains latched outs, no need for external 150ms latch time) respectively.
     
  5. vinodquilon

    Member

    Dec 24, 2009
    234
    0
    I have lot of discussions about this subject. See the link,
    http://www.electro-tech-online.com/...1549-device-control-using-telephone-dtmf.html
     
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