I'm going to receive audio data from a device and handle through mobile's headphone jack. but my data has low frequency about 1Hz and depending what i found its too low for this port, I searched about 3.5mm headphone jack frequency range but couldn't find anything! what is your suggestion? USB port can solve the problem?

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    \$\begingroup\$ How could anyone know how to help you given what information you have provided. Also, check out the following guidelines regarding questions like this: electronics.stackexchange.com/help/on-topic - note the "not about" section. \$\endgroup\$ – Andy aka Oct 14 '14 at 8:40
  • \$\begingroup\$ We speak English here. If you can't, get someone that does or don't post here. \$\endgroup\$ – Olin Lathrop Oct 14 '14 at 13:41
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    \$\begingroup\$ @OlinLathrop ooookkk!!! thanks for your advise Mr. Lathrop. you are very angry! \$\endgroup\$ – mojtaba Oct 14 '14 at 15:34
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    \$\begingroup\$ It's not the 3.5mm jack which is imposing the lower frequency limit, it's the device its a part of which will have a limited capability in that area. The jack itself will quite happily pass frequencies all the way down to 0Hz (DC). \$\endgroup\$ – brhans Oct 15 '14 at 2:06
  • \$\begingroup\$ @brhans thank you. i think using 3.5mm jack is almost complicated and needs more research. what do you think about using USB? Implementation is easier? supports low frequency? \$\endgroup\$ – mojtaba Oct 16 '14 at 17:37

Your question is very nearly incoherent. You do not say (clearly) whether you want to put data into the cell phone and analyse it there, or whether you are going to send data out of the cell phone to be analysed by an external system.

Regardless, certain parts of your question can be answered.

  1. The audio range of the earphone of a cell phone can't be counted on to go below 100Hz - some phones will go lower, some will not even get down to 100Hz.
  2. The audio range of the microphone of a cell phone can't be counted on to go below 100Hz - some phones will go lower, some will not even get down to 100Hz.
  3. The phone itself will not convert from some nebulous, undefined "data" to audio or from audio back to data - your software will have to do that.

To work around the limitations of the cellphone audio, you would be better advised to modulate the data on to an audio frequency that the phone can handle - in the middle of the speech band is probably best, so 1200Hz to 1800Hz. You can find plenty of data on the internet about frequency shift keying (FSK) or phase shift keying (PSK) for transmitting data across audio systems.

If none of that made sense, then you have a long way to go before you begin working on your data transmission. Read up on things. Define your data format and data rate. See what you can come up with for ways to achieve your goal. If you get stuck, come back and write a better question - and consider telling us what you are trying to do, as someone here may have done it already and can point you at a better way.


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