diff --git a/pom.xml b/pom.xml
index a9d058fe..c0cf6d17 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,7 +4,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>org.pamguard</groupId>
   <artifactId>Pamguard</artifactId>
-  <version>2.02.13a</version>
+  <version>2.02.13b</version>
   <name>Pamguard</name>
   <description>Pamguard using Maven to control dependencies</description>
 	<url>www.pamguard.org</url>
diff --git a/src/PamController/PamguardVersionInfo.java b/src/PamController/PamguardVersionInfo.java
index b581b14a..576632d2 100644
--- a/src/PamController/PamguardVersionInfo.java
+++ b/src/PamController/PamguardVersionInfo.java
@@ -31,12 +31,12 @@ public class PamguardVersionInfo {
 	 * Version number, major version.minorversion.sub-release.
 	 * Note: can't go higher than sub-release 'f'
 	 */
-	static public final String version = "2.02.13a";
+	static public final String version = "2.02.13b";
 	
 	/**
 	 * Release date
 	 */
-	static public final String date = "27 August 2024";
+	static public final String date = "September 2024";
 	
 //	/**
 //	 * Release type - Beta or Core
diff --git a/src/help/utilities/tethys/docs/tethys_overview.html b/src/help/utilities/tethys/docs/tethys_overview.html
index 6e9e6515..6d4904f9 100644
--- a/src/help/utilities/tethys/docs/tethys_overview.html
+++ b/src/help/utilities/tethys/docs/tethys_overview.html
@@ -32,8 +32,12 @@ img {
   
   <p>
     PAMGuard is compatible
-    with <a href="https://tethys.sdsu.edu/tethys3/">Tethys 3.0</a> or
-    later.
+    with <a href="https://doi.org/10.5281/zenodo.13626338">Tethys 3.1</a> or
+    later available for download from <a href="https://doi.org/10.5281/zenodo.13626338">Zenodo.</a>
+    </p>
+    <p>
+
+    
     <a href="https://tethys.sdsu.edu/">Tethys</a> is a freely
     available open source temporal-spatial database for metadata
     related to acoustic recordings. The database is intended to house
diff --git a/src/soundPlayback/PlaybackProcess.java b/src/soundPlayback/PlaybackProcess.java
index 6d488ef9..96bbc3be 100644
--- a/src/soundPlayback/PlaybackProcess.java
+++ b/src/soundPlayback/PlaybackProcess.java
@@ -71,6 +71,7 @@ public class PlaybackProcess extends PamInstantProcess {
 //		super.prepareProcess();
 //		System.out.println("Playback prepare process");
 		prepareProcess(getSourceSampleRate());
+		remainDelayMillis = 0;
 	}
 	
 	public boolean prepareProcess(double sourceSampleRate) {
@@ -204,7 +205,10 @@ public class PlaybackProcess extends PamInstantProcess {
 
 	@Override
 	synchronized public void newData(PamObservable o, PamDataUnit arg) {
-		if (playbackControl.playbackSystem == null) return;
+		if (playbackControl.playbackSystem == null) {
+			runSpeedLimit(o, arg);
+			return;
+		}
 		int channel = PamUtils.getSingleChannel(arg.getChannelBitmap());
 		int pos = channelPos[channel];
 //		System.out.printf("Channel %d, pos %d\n", channel, pos);
@@ -233,6 +237,7 @@ public class PlaybackProcess extends PamInstantProcess {
 				boolean playOK = playbackControl.playbackSystem.playData(playUnits, 1);
 				if (!playOK) {
 					playWarning.setWarning("PlaybackProcess: playData return error", 2);
+					runSpeedLimit(o, arg);
 					noteNewSettings(); // forces full reset of playback
 				}
 				else {
@@ -255,6 +260,43 @@ public class PlaybackProcess extends PamInstantProcess {
 //		}
 	}
 
+	double remainDelayMillis = 0;
+	/**
+	 * Modern desktops won't show a soundcard if no headphones are connected
+	 * or plugged in. e.g. the ones in the teachinglab at work. In this case it's
+	 * almost impossible to run the tutorials since everything happens so fast. 
+	 * So this function will cause a small delay before returning when no 
+	 * devices are present.  
+	 * @param o
+	 * @param arg
+	 */
+	private void runSpeedLimit(PamObservable o, PamDataUnit arg) {
+		Double dataMillis = arg.getDurationInMilliseconds();
+		if (dataMillis == null) {
+			return;
+		}
+		double speed = playbackControl.playbackParameters.getPlaybackSpeed();
+		double delay = dataMillis / speed;
+		int intDelay = (int) Math.floor(delay);
+		/*
+		 * Be a bit anal and deal with non integer bits by randomly chosing 
+		 * to add an extra milli or not. 
+		 */
+		double remainder = delay - intDelay;
+		remainDelayMillis += remainder;
+		while (remainDelayMillis > 1) {
+			intDelay++;
+			remainDelayMillis--;
+		}
+		if (intDelay > 0) {
+			try {
+				Thread.sleep(intDelay);
+			} catch (InterruptedException e) {
+				e.printStackTrace();
+			}
+		}
+	}
+
 	private RawDataUnit[] preprocessData(RawDataUnit[] inputDataUnits) {
 		int isNull = 0;
 		RawDataUnit[] outUnits = new RawDataUnit[inputDataUnits.length];
diff --git a/src/soundPlayback/SoundCardPlaybackBase.java b/src/soundPlayback/SoundCardPlaybackBase.java
index de167b22..7618d2e4 100644
--- a/src/soundPlayback/SoundCardPlaybackBase.java
+++ b/src/soundPlayback/SoundCardPlaybackBase.java
@@ -94,10 +94,9 @@ public class SoundCardPlaybackBase {
 			// give up if there are no mixers on the system
 			return false;
 		}
-		if (deviceNumber >= mixerinfos.size()) {
+		if (deviceNumber >= mixerinfos.size() || deviceNumber < 0) {
 			deviceNumber = 0;// reset to default device. 
 		}
-		
 		Mixer.Info thisMixerInfo = mixerinfos.get(deviceNumber);
 		currentMixer = AudioSystem.getMixer(thisMixerInfo);
 		if (currentMixer.getSourceLineInfo().length <= 0){