diff --git a/plugins/samplesink/limesdroutput/limesdroutputgui.ui b/plugins/samplesink/limesdroutput/limesdroutputgui.ui
index ef0755699..ca347eea3 100644
--- a/plugins/samplesink/limesdroutput/limesdroutputgui.ui
+++ b/plugins/samplesink/limesdroutput/limesdroutputgui.ui
@@ -280,6 +280,20 @@
        </property>
       </spacer>
      </item>
+     <item>
+      <widget class="QToolButton" name="extClock">
+       <property name="toolTip">
+        <string>External clock source selection</string>
+       </property>
+       <property name="text">
+        <string/>
+       </property>
+       <property name="icon">
+        <iconset resource="../../../sdrgui/resources/res.qrc">
+         <normaloff>:/clocksource.png</normaloff>:/clocksource.png</iconset>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>
diff --git a/plugins/samplesource/limesdrinput/limesdrinputgui.ui b/plugins/samplesource/limesdrinput/limesdrinputgui.ui
index b15ecd167..69170950d 100644
--- a/plugins/samplesource/limesdrinput/limesdrinputgui.ui
+++ b/plugins/samplesource/limesdrinput/limesdrinputgui.ui
@@ -325,6 +325,20 @@
        </property>
       </widget>
      </item>
+     <item>
+      <widget class="ButtonSwitch" name="extClock">
+       <property name="toolTip">
+        <string>External clock source selection</string>
+       </property>
+       <property name="text">
+        <string/>
+       </property>
+       <property name="icon">
+        <iconset resource="../../../sdrgui/resources/res.qrc">
+         <normaloff>:/clocksource.png</normaloff>:/clocksource.png</iconset>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>
diff --git a/sdrgui/resources/clocksource.png b/sdrgui/resources/clocksource.png
new file mode 100644
index 000000000..4dbbffbc9
Binary files /dev/null and b/sdrgui/resources/clocksource.png differ
diff --git a/sdrgui/resources/res.qrc b/sdrgui/resources/res.qrc
index ce9b3853b..db0578237 100644
--- a/sdrgui/resources/res.qrc
+++ b/sdrgui/resources/res.qrc
@@ -80,5 +80,6 @@
         <file>antenna.png</file>
         <file>link.png</file>
         <file>choose.png</file>
+        <file>clocksource.png</file>
     </qresource>
 </RCC>