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Seperating DTMF Signal and Tones

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Hi.

I'm trying to seperate DTMF signals(DTMF IN) from DTMF tones(DT) and found a circuit that does it using a transformer. However i don't understand how i could connect it like shown in the diagram. It would be better if i could connect it using an off the shelf chip to do the same. Thanks.
 

Attachments

  • Seperating DTMF IN and DT.jpg
    Seperating DTMF IN and DT.jpg
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If DT is dial tone, then why would a telephone produce a dial tone?
DTMF is the dual frequency tones produced by a touch-tone dial on a telephone.

The transformer mixes the two signals together, it does not separate them.
 
dramrattan, You have some confusion or inability to express your request. Please try again to explain with more detail, and include the country location to try to discern what type of tones are used in that country telephony system.

Are you trying to separate each of the single tones that together form the dual tone or just to know which are the two tones present in each dual tone heard ?

Miguel
 
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Seperating DTMF

The two tones are a combination of the row frequency and column frequency if i'm correct. I'm from Trinidad and the RJ11 phone jack is what is used in our country. What i was trying to understand is how to extract DTMF using hardware not software from the RING and TIP lines. I saw in the diagram attached where the transformer's primary side was connected to the RING and TIP lines and then the secondary side split the signal into two parts namely DTMF IN which goes to a DTMF decoder MT8870 and a DT(dialog tones) signal which goes to a multivibrator tone generator, the LM555N for use of verification of a correct code sequence entered by a user using a DTMF phone which is suppose to activate an electrical device. I'm trying to used to phone line to monitor duration, caller ID & the blocking of specific incoming/outgoing calls that the user desire as well as control some electrical device like an air conditioner using these extracted DTMF signals.

Thus if *1 suppose to activate the device and *1 is pressed on the DTMF phone, the LM555N will generate a beep that will be heard via this DT pin. Likewise if a wrong combination is entered on the phone like *2, two beeps would be heard indicating to the user that combination is wrong via this same DT pin. I also attached the circuit showing the LM555N multivibrator.

I would like to know how to hook up the secondary side of the tranformer as shown in the diagram to split the signals into DTMF IN and DT as shown. Does the transformer come with connections where i could split the output into two like shown in the diagram? Or, is there another way to this same thing rather than using a transformer?

Hope this makes it better to understand what i'm trying to understand.
 

Attachments

  • DTMF Decoder.jpg
    DTMF Decoder.jpg
    187.8 KB · Views: 270
  • Seperating DTMF IN and DT.jpg
    Seperating DTMF IN and DT.jpg
    198.5 KB · Views: 206
  • Tone generator to indicate access to external device.jpg
    Tone generator to indicate access to external device.jpg
    179.2 KB · Views: 260
Your circuit should work fine.
The square-wave from the 555 will sound raspy like a square-wave and will probably be much too loud.
 
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