* <td>When defined, this alters the demo to produce a square wave test tone when the first board button is pressed
* instead of sampling the board microphone.</td>
* </tr>
* <tr>
* <td>MICROPHONE_BIASED_TO_HALF_RAIL</td>
* <td>When defined, this alters the demo to produce a square wave test tone when the first board button is pressed
* instead of sampling the board microphone.</td>
* </tr>
* <tr>
* <td>MICROPHONE_BIASED_TO_HALF_RAIL</td>