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I was doing some research, on how telephone works, and I found that when user, click numbers they are converted to frequency and passed to wire. I want to know how the frequency generator work, what is it's official known as and what frequency range it work under?

One more thing, when user click number does it convert to signal and send to wire or when 10 digits are pressed then that group is converted to signal and passed to wire?

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What you are referring to is called DTMF or "dual-tone, multiple-frequency" or simply tone-dialling.

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Figure 1. DTMF table. Pressing a button causes simultaneous generation of two tones - the row tone and the column tone. Source: Wikipedia, dual-tone multi-frequency signalling.

Note that the tones are chosen to be not harmonically related.

When user click number does it convert to signal and send to wire or when 10 digits are pressed then that group is converted to signal and passed to wire?

If you test this on a landline phone you will hear the tones generated simultaneously with the button press and for as long as the button is held. In any case, the telephone does not know how many digits long a phone number will be.

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  • \$\begingroup\$ So, if I click 1, then what will be the final frequency sent for it? Will it be 697 Hz + 1209 Hz, 697 Hz or 1209 Hz? \$\endgroup\$ Apr 4 '16 at 6:54
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    \$\begingroup\$ @GauravDave the clue is in the phrase "dual-tone" \$\endgroup\$
    – Andy aka
    Apr 4 '16 at 7:07
  • \$\begingroup\$ @Andyaka Sorry, but I don't have electronics background. So does 697Hz Frequency signal is sent and then 1209 Hz or 1906Hz is sent to cable? \$\endgroup\$ Apr 4 '16 at 7:12
  • \$\begingroup\$ Read the answer, it is 100% clear. \$\endgroup\$
    – Andy aka
    Apr 4 '16 at 7:13
  • \$\begingroup\$ @GauravDave dual-tone means that two tones are generated at the same time. \$\endgroup\$
    – Steve G
    Apr 4 '16 at 7:50

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