| page.title=FunPlug Audio Dongle |
| @jd:body |
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| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol id="auto-toc"> |
| </ol> |
| </div> |
| </div> |
| |
| <p> |
| The diagram and photo below show an audio loopback |
| <a href="http://en.wikipedia.org/wiki/Dongle">dongle</a> |
| for the |
| <a href="http://en.wikipedia.org/wiki/Phone_connector_(audio)">headset connector</a> |
| that we call the "FunPlug." |
| The Chrome hardware team designed this circuit and plug for functional testing; |
| however it has many other uses too. The Android audio team uses it to measure |
| <a href="audio_latency_measure.html#measuringRoundTrip">round-trip audio latency</a>, |
| via the Larsen effect (feedback loop). |
| </p> |
| |
| <h2 id="funplugCircuit">FunPlug circuit</h2> |
| |
| <img src="audio/images/funplug_circuit.png" alt="FunPlug circuit" /> |
| |
| <p> |
| To ensure that the output signal will not overload the microphone input, |
| we cut it down by about 20dB. |
| The resistor loads are there to tell the microphone polarity switch that |
| it is a US/CTIA pinout plug. |
| </p> |
| |
| <h2 id="funplugAssembled">FunPlug assembled</h2> |
| |
| <img src="audio/images/funplug_assembled.jpg" alt="FunPlug fully assembled" /> |
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