I didn't know where to ask this; I hope it's in the proper place.

My wife just bought one of these mobile credit card processing devices for her phone and I was curious as to why these devices use TRRS instead of the Micro USB connection.

Could it be as simple as a more stable, physical, attachment to the frame of the phone?

1 Answer 1


Probably because many mobile devices don't have micro-USB ports, but almost all of them (iPhones, iPads, Android phones, etc.) have headset (TRRS) jacks.

This allows the mobile credit card processing company to make a single hardware device that will work with all of these mobile devices.

  • 1
    After thinking about your reply, and then thinking about Apple hardware; I think perhaps you might be correct. Since Apple doesn't have standard "anything" /sarc, making use of the TRRS (standard) simplified the products such that they only have to have one technical build. This makes sense.
    – Hardrada
    Commented Apr 5, 2016 at 13:55
  • No need to bash Apple, there are gazillions other phones and there is not a single port implemented on, say, more than 30% of them. Commented Apr 6, 2016 at 0:23
  • Having no port is not the same as having a port that is proprietary. One would simply be incompatible by omission and the other incompatible by design.
    – Hardrada
    Commented Apr 9, 2016 at 1:16

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