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When listening to FM radio on mobile using 3.5 jack headphone , sometimes the name of current show or other "xyz" information are displayed, how is that possible?

How do analog signals contain that information and how does a mobile phone identify such data from all mixed signals and show that differently?

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  • \$\begingroup\$ Was just thinking about this the other day, great question! \$\endgroup\$ – Kevin Mark Sep 19 '13 at 3:17
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The system responsible for this is called Radio Data System (RDS).

What you likely see is the Programme Service or Radio Text data.

Another very common use of RDS is the traffic function of in car radios, which always seems to assume that you need to hear the traffic news much louder than everything else on the radio.

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  • \$\begingroup\$ Beside this, sometimes when i connect any good company's headphone like "bose" to 3.5 jack, it gets recognized by the computer. How is that possible? Can MCU in headphone store or send such data over 3.5 jack? \$\endgroup\$ – Vish Sep 18 '13 at 14:22
  • \$\begingroup\$ @VishveshShah what mcu in the headphone? I've never heard of any headphones with a microcontroller in them. \$\endgroup\$ – Passerby Sep 18 '13 at 14:39
  • \$\begingroup\$ Sorry to sound sceptical, but I have never head of data being sent alongside stereo audio on a standard TRS connector, even if the headphones had an MCU to send that data I highly doubt the PC is capable of reading it. \$\endgroup\$ – Dan Nixon Sep 18 '13 at 14:55
  • \$\begingroup\$ i think you should ask another question about the headset. but generally, as devices contain more and more circuitry, and manufacturers have agreed on standard coding, more and more devices have been able to be identified by the host system. \$\endgroup\$ – Andyz Smith Sep 18 '13 at 15:10
  • \$\begingroup\$ @DanNixon Consider the scenario of Radio Data System. Controller or any memory device implemented in headphone which sends that data. So how data read on our car player by RDS that exact way computer can read the data...wouldn't it be possible?..or am i missing any important thing? \$\endgroup\$ – Vish Sep 18 '13 at 15:51
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Many radio stations in the US have moved to a hybrid analog/ digital system known as IBOC, In Band On Channel. The entertainment program is transmitted in both digital and analog, for backwards compatibility reasons, with the digital portion being 'sandwiched' near the originally assigned frequency, but, miraculously, not interfering with it. The new digital signal can be used to present the entertainment program stream digitally as well as other digital information like station, and song identification.

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    \$\begingroup\$ Engineering is not exactly a miracle as it is proper understanding of physical phenomena and leveraging it \$\endgroup\$ – Gustavo Litovsky Sep 18 '13 at 15:35
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    \$\begingroup\$ well i'll go with Arthur C. Clarke who says that any sufficiently advanced technology is indistiguishable from magic. and i say miraculously, with a bit of sarcasm, because we all know that there is interference in that RF envelope now. \$\endgroup\$ – Andyz Smith Sep 18 '13 at 15:39

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