Power Over Audio

An obsolete Intuit / Roam Data credit card reader emerged from the heap:

Intuit Roam Data Reader

Intuit Roam Data Reader

“Turn up the volume” suggestes where the power comes from:

Intuit Roam Data Reader - plug wiring

Intuit Roam Data Reader – plug wiring

They drive a LOUD, probably square-ish, audio signal through both “earphone”channels, rectify and regulate the output, and have plenty of power for the reader. The card data returns through the “mic” as another audio signal; I assume they choose an encoding well-suited for a dab of DSP decoding.

Nowadays, of course, 3.5 mm jacks are obsolete, audio data travels by Bluetooth, and you must keep a myriad of batteries charged at all times.

  1. #1 by Olli on 2018-11-04 - 15:21

    “audio data travels by Bluetooth”

    And money too…

    • #2 by Ed on 2018-11-04 - 19:43

      Maybe the money just leaks out? [sigh]

  2. #3 by Olli on 2018-11-06 - 02:46

    “3.5 mm jacks are obsolete”

    “If it’s good enough for Granddad It’s good enough for me.”

    • #4 by Ed on 2018-11-06 - 07:41

      Given my deflicted hearing, Bluetooth definitely isn’t the limiting factor.

      Indeed, I can’t hear any difference between CD-quality and low-bit-rate audio …