Docs: Update Wired audio headset specification
Bug: 18459401
Change-Id: Ief9375f1364acfa95dd65e85c0e98d8695c197b3
diff --git a/src/accessories/headset-spec.jd b/src/accessories/headset-spec.jd
index d87c19a..c9a749e 100644
--- a/src/accessories/headset-spec.jd
+++ b/src/accessories/headset-spec.jd
@@ -24,7 +24,7 @@
</div>
</div>
-<p><em>Version 1.0</em></p>
+<p><em>Version 1.1</em></p>
<p>This document specifies the requirements for headsets and mobile devices to
function uniformly across the Android ecosystem. It is separated into two
@@ -127,7 +127,7 @@
<p>Optional</p>
</td>
<td>
-<p>Reserved (Nexus devices will use this reserved function to launch Google Now
+<p>Reserved (Nexus devices will use this reserved function to launch Google
voice search)</p>
</td>
</tr>
@@ -284,25 +284,40 @@
</tr>
</table>
+<p>In the following diagrams, Button A is mapped to Function A, Button B to
+Function B, and so on.</p>
+
<h3 id=reference_headset_test_circuit_1>Reference Headset Test Circuit 1</h3>
<img src="images/headset-circuit1.png" alt="Reference Headset Test Circuit 1" />
<p class="img-caption"><strong>Figure 1.</strong> Reference headset test circuit 1</p>
-<p class="note"><strong>Note:</strong> Four-segment plug shows CTIA pinout. For
-OMTP pinout, please swap MIC and GND segments.</p>
+<p class="note"><strong>Note:</strong> The above diagram shows the CTIA pinout
+for a 4-segment plug. For the OMTP pinout, switch the positions of the MIC and
+GND segments.</p>
<h3 id=reference_headset_test_circuit_2>Reference Headset Test Circuit 2</h3>
+<p>The second reference circuit shows how the actual resistor values (R1 - R4)
+are altered to meet this specification.</p>
+
<img src="images/headset-circuit2.png" alt="Reference Headset Test Circuit 2" />
<p class="img-caption"><strong>Figure 2.</strong> Reference headset test circuit 2</p>
-<p class="note"><strong>Note:</strong> The second reference circuit above
-illustrates how the actual resistor values (R1 - R4) will change based on the
-microphone capsule resistance to achieve the equivalent impedance values as
-required by the specification. The example above assumes a 5 kOhm microphone
-impedance. Therefore, as an example, to achieve an equivalent R4 impedance of
-135 Ohm, the actual R4 resistor value needs to be 139 Ohms.</p>
+<p>The actual resistance of the buttons parallel with the microphone (R1-R4) is
+based on the microphone capsule resistance (Rmic) and the equivalent impedance
+values (ReqA-ReqD). Use the following formula:</p>
+
+<p><em>Rn=(Rmic*ReqN) / (ReqN-Rmic)</em></p>
+
+<p>Where R<em>n</em> is the actual resistance of a button, Req<em>N</em> is the
+equivalent impedance value of that button (provided), and Rmic is the
+microphone impedance value.</p>
+
+<p>The example above assumes a 5 kohm microphone impedance (Rmic). Therefore, to
+achieve an equivalent R4 impedance of 135 ohm (ReqD), the actual resistor value
+(R4) needs to be 139 ohms.</p>
+
<h2 id=mobile_device_jack_specifications>Mobile Device (Jack) Specifications</h2>
@@ -548,7 +563,7 @@
</tr>
<tr>
<td>
-<p>Minimum output voltage drive capacity </p>
+<p>Maximum output voltage drive</p>
</td>
<td>
<p>150mV </p>
diff --git a/src/accessories/images/headset-circuit1.png b/src/accessories/images/headset-circuit1.png
index c69df98..f3e622a 100644
--- a/src/accessories/images/headset-circuit1.png
+++ b/src/accessories/images/headset-circuit1.png
Binary files differ
diff --git a/src/accessories/images/headset-circuit2.png b/src/accessories/images/headset-circuit2.png
index 67bd5b4..ff6b541 100644
--- a/src/accessories/images/headset-circuit2.png
+++ b/src/accessories/images/headset-circuit2.png
Binary files differ
