diff --git a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
index 8a8a7aa16..7e7ea9718 100644
--- a/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
+++ b/TBF/BenchControl/TestMethods/iPerlCommunication/iPerlHead/IperlHead.cs
@@ -343,7 +343,8 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
         double timestampSecEnd2;
 		double timestampSecEnd3;
 
-        private int telegramIx;
+        int currentTelegramIx;
+        bool startSampleAcquired;
         public int TestStartTelegramIx;
         public int TestEndTelegramIx;
 
@@ -548,6 +549,8 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 
 			/// Reset opto data
 			optoDataCount = 0;
+            currentTelegramIx = -1;
+            startSampleAcquired = false;
             TestStartTelegramIx = 0;
             TestEndTelegramIx = 0;
 
@@ -584,12 +587,13 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 		{
             sampleNr++;
 			ReadPulses();
-            if (sampleNr == 4)
+            if (!startSampleAcquired && (sampleNr >= 4) && (currentTelegramIx >= 0))
             {
 				/// Take the test start sample
+                startSampleAcquired = true;
                 volumeLtrStart = volumeLtr;
                 timestampSecStart = timestampSec;
-                TestStartTelegramIx = telegramIx;
+                TestStartTelegramIx = currentTelegramIx;
             }
 
             /// Shift data in pipelines
@@ -603,7 +607,10 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 			timestampSecEnd2 = timestampSecEnd1;
 			timestampSecEnd1 = timestampSec;
 
-            TestEndTelegramIx = telegramIx - 3;
+            if (startSampleAcquired && (currentTelegramIx >= 3))
+            {
+                TestEndTelegramIx = currentTelegramIx - 3;
+            }
 
 			return Event.ReadRegisterDone;
 		}
@@ -851,7 +858,7 @@ namespace TBF.BenchControl.TestMethods.iPerlCommunication.iPerlHead
 
         void OptoTelegramRreceived(int currentIx, bool async, Int64 volumeRawExt, Int64 timestampRawExt)
 		{
-            telegramIx = currentIx;
+            currentTelegramIx = currentIx;
 
             lastVolumeRaw = volumeRawExt;
             lastTimestamp = timestampRawExt;