diff --git a/GSM/GSML1FEC.cpp b/GSM/GSML1FEC.cpp
index d3db880..71cadba 100644
--- a/GSM/GSML1FEC.cpp
+++ b/GSM/GSML1FEC.cpp
@@ -243,6 +243,7 @@ void L1Encoder::rollForward()
 	// This implements GSM 05.02 Clause 7 for the transmit side.
 	mPrevWriteTime = mNextWriteTime;
 	mTotalFrames++;
+	ScopedLock lock(mWriteTimeLock,__FILE__,__LINE__);	// (pat) Protects getNextWriteTime.
 	mNextWriteTime.rollForward(mMapping.frameMapping(mTotalFrames),mMapping.repeatLength());
 }
 
@@ -316,7 +317,6 @@ const L1Decoder* L1Encoder::sibling() const
 	return mParent->decoder();
 }
 
-
 void L1Encoder::resync(bool force)
 {
 	// If the encoder's clock is far from the current BTS clock,
@@ -328,11 +328,20 @@ void L1Encoder::resync(bool force)
 		mNextWriteTime = now;
 		mNextWriteTime.TN(mTN);
 		mTotalFrames = 0;	// (pat 4-2014) Make sure we start at beginning of mapping.
-		mNextWriteTime.rollForward(mMapping.frameMapping(mTotalFrames),mMapping.repeatLength());
+		{ ScopedLock lock(mWriteTimeLock,__FILE__,__LINE__);	// (pat) Protects getNextWriteTime.
+		  mNextWriteTime.rollForward(mMapping.frameMapping(mTotalFrames),mMapping.repeatLength());
+		}
 		OBJLOG(DEBUG) <<"L1Encoder RESYNC "<< " next=" << mNextWriteTime << " now=" << now;
 	}
 }
 
+Time L1Encoder::getNextWriteTime()
+{
+	resync();
+	ScopedLock lock(mWriteTimeLock,__FILE__,__LINE__);
+	return mNextWriteTime;
+}
+
 
 void L1Encoder::waitToSend() const
 {
@@ -2279,7 +2288,9 @@ void TCHFACCHL1Encoder::dispatch()
 	// Most channels do not need this, becuase they are entirely data-driven
 	// from above.  TCH/FACCH, however, must feed the interleaver on time.
 	if (!encActive()) {
-		mNextWriteTime += 26;
+		{ ScopedLock lock(mWriteTimeLock,__FILE__,__LINE__);	// (pat) Protects getNextWriteTime.
+		  mNextWriteTime += 26;
+		}
 		gBTS.clock().wait(mNextWriteTime);
 		return;
 	}
diff --git a/GSM/GSML1FEC.h b/GSM/GSML1FEC.h
index 28783b8..bdc83dd 100644
--- a/GSM/GSML1FEC.h
+++ b/GSM/GSML1FEC.h
@@ -110,6 +110,7 @@ class L1Encoder {
 	//@}
 
 	/**@name Multithread access control and data shared across threads. */
+	// (pat) It is not being used effectively.
 	//@{
 	mutable Mutex mEncLock;
 	//@}
@@ -127,6 +128,9 @@ class L1Encoder {
 	GSM::Time mPrevWriteTime;		///< timestamp of previous generated burst
 	GSM::Time mNextWriteTime;		///< timestamp of next generated burst
 
+	// (pat 10-2014) Another thread calls getNextWriteTime so we must protect places that write to mNextWriteTime.
+	mutable Mutex mWriteTimeLock;
+
 	volatile bool mRunning;			///< true while the service loop is running
 	Bool_z mEncActive;				///< true between open() and close()
 	Bool_z mEncEverActive;			// true if the encoder has ever been active.
@@ -210,7 +214,7 @@ class L1Encoder {
 	const L1FEC* parent() const { return mParent; }
 	L1FEC* parent() { return mParent; }
 
-	GSM::Time getNextWriteTime() { resync(); return mNextWriteTime; }
+	GSM::Time getNextWriteTime();
 
 	protected: