diff --git a/audio.h b/audio.h
index fdf4210..6e2e93c 100644
--- a/audio.h
+++ b/audio.h
@@ -30,11 +30,17 @@ enum ptt_method_e {
 	PTT_METHOD_SERIAL,	/* Serial port RTS or DTR. */
 	PTT_METHOD_GPIO,	/* General purpose I/O, Linux only. */
 	PTT_METHOD_LPT,	    /* Parallel printer port, Linux only. */
-    PTT_METHOD_HAMLIB,  /* HAMLib, Linux only. */
-    PTT_METHOD_AUDIO }; /* Audio channel. */
+  PTT_METHOD_HAMLIB,  /* HAMLib, Linux only. */
+  PTT_METHOD_AUDIO }; /* Audio channel. */
 
 typedef enum ptt_method_e ptt_method_t;
 
+enum ptt_audio_state_e {
+  PTT_AUDIO_STATE_STOP,
+  PTT_AUDIO_STATE_START,
+  PTT_AUDIO_STATE_CLOSE };
+typedef enum ptt_audio_state_e ptt_audio_state_t;
+
 enum ptt_line_e { PTT_LINE_NONE = 0, PTT_LINE_RTS = 1, PTT_LINE_DTR = 2 };	  //  Important: 0 for neither.	
 typedef enum ptt_line_e ptt_line_t;
 
@@ -196,14 +202,16 @@ struct audio_s {
 	        int ptt_invert;		/* Invert the output. */
 	        int ptt_invert2;	/* Invert the secondary output. */
 
-            int ptt_channel;    /* Channel number for audio PTT. */
-            int ptt_frequency;  /* Audio frequency for audio PTT. */
+          int ptt_channel;    /* Channel number for audio PTT. */
+          int ptt_frequency;  /* Audio frequency for audio PTT. */
 #if __WIN32__
-            HANDLE ptt_start;   /* Handle for event that starts ptt tone. */
-            HANDLE ptt_stop;    /* Handle for event that stops ptt tone. */
-            HANDLE ptt_close;   /* Handle for event that closes ptt. */
+          HANDLE ptt_start;   /* Handle for event that starts ptt tone. */
+          HANDLE ptt_stop;    /* Handle for event that stops ptt tone. */
+          HANDLE ptt_close;   /* Handle for event that closes ptt. */
 #else
-
+          pthread_mutex_t ptt_mutex;    /* Mutex for controlling ptt tone state. */
+          pthread_cond_t ptt_condition; /* Condition for controlling ptt tone state. */
+          ptt_audio_state_t ptt_state;  /* State of ptt tone. */
 #endif
 
 #ifdef USE_HAMLIB
diff --git a/audio_ptt.c b/audio_ptt.c
index ae91e3f..19bc4fd 100644
--- a/audio_ptt.c
+++ b/audio_ptt.c
@@ -91,67 +91,64 @@ static void * ptt_thread (void *arg)
 
 	  err = snd_pcm_open(&handle, save_audio_config_p->adev[a].adevice_out, SND_PCM_STREAM_PLAYBACK, 0);
 	  if (err == 0) {
-		  snd_pcm_sframes_t frames;
 		  snd_pcm_format_t format = SND_PCM_FORMAT_S16_LE;
 
 	    err = snd_pcm_set_params(handle, format, SND_PCM_ACCESS_RW_INTERLEAVED,
 			                  save_audio_config_p->adev[a].num_channels,
 			                  save_audio_config_p->adev[a].samples_per_sec, 1, 500000);
   	  if (err == 0) {
-		    short* pnData;
+ 		    short* pnData;
 		    short sample;
-		    int nSamples = save_audio_config_p->adev[a].samples_per_sec / 10;
+		    int nSamples = save_audio_config_p->adev[a].samples_per_sec / 5;
 		    int nBufferLength = save_audio_config_p->adev[a].num_channels * nSamples * sizeof(short);
 		    int i;
+        int j;
 
 		    pnData = (short*)malloc (nBufferLength);
 
-		    if (save_audio_config_p->adev[a].num_channels == 1) {
-			    for (i = 0; i < nSamples; i++) {
-			      sample = (short)( (double)SHRT_MAX * sin( ( (double)i * freq / (double)save_audio_config_p->adev[a].samples_per_sec ) * 2.0 * M_PI ) );
-			      pnData[i] = sample;
+  	    for (i = 0; i < nSamples; i++) {
+	        sample = (short)( (double)SHRT_MAX * sin( ( (double)i * freq / (double)save_audio_config_p->adev[a].samples_per_sec ) * 2.0 * M_PI ) );
+			      
+          for (j = 0; j < save_audio_config_p->adev[a].num_channels; j++) {
+  	        if (channel == ADEVFIRSTCHAN( a ) + j) {
+              pnData[i*save_audio_config_p->adev[a].num_channels + j] = sample;
+            } else {
+  		        pnData[i*save_audio_config_p->adev[a].num_channels + j] = 0;
+            }
 			    }
 		    }
-		    else {
-			    for (i = 0; i < nSamples; i++) {
-			      sample = (short)( (double)SHRT_MAX * sin( ( (double)i * freq / (double)save_audio_config_p->adev[a].samples_per_sec ) * 2.0 * M_PI ) );
-			      if (channel == ADEVFIRSTCHAN( a )) {
+        
+        while (1) {
+          pthread_mutex_lock (&save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_mutex);
+          ptt_audio_state_t ptt_state = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_state;
+          pthread_mutex_unlock (&save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_mutex);
 
-			        // Stereo, left channel.
+          if (ptt_state == PTT_AUDIO_STATE_STOP) {
+            snd_pcm_drop (handle);
 
-			        pnData[i*2 + 0] = sample;
-			        pnData[i*2 + 1] = 0;
-			      }
-			      else {
+            pthread_mutex_lock (&save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_mutex);
+            pthread_cond_wait (&save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_condition, &save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_mutex);
+            ptt_state = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_state;
+            pthread_mutex_unlock (&save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_mutex);
 
-			        // Stereo, right channel.
+            if (ptt_state == PTT_AUDIO_STATE_START) {
+              snd_pcm_prepare (handle); 
+            }
+          }
+         
+          if (ptt_state == PTT_AUDIO_STATE_START) {
+    		    snd_pcm_writei (handle, pnData, nSamples);
+          }
+          else if (ptt_state == PTT_AUDIO_STATE_CLOSE) {
+            snd_pcm_drop (handle);
 
-			        pnData[i*2 + 0] = 0;
-			        pnData[i*2 + 1] = sample;
-			      }
-			    }
-		    }       
-		    
-		    //
-		    // ptt_set on
-		    //
-
-		    for (i=0; i<50; i++) {
-			    frames = snd_pcm_writei(handle, pnData, nSamples);
-		    }
-
-		    //
-		    // ptt_set off
-		    //
-
-		    //
-		    // close
-		    //
+            break;
+          }
+        }
 
 		    free (pnData);
 		  }
-
-		  snd_pcm_close(handle);
+		  snd_pcm_close (handle);
 	  }
 #else
     int oss_audio_device_fd;
@@ -165,3 +162,4 @@ static void * ptt_thread (void *arg)
 }
 
 #endif
+
diff --git a/audio_ptt_win.c b/audio_ptt_win.c
index 92c0c50..e690ea4 100644
--- a/audio_ptt_win.c
+++ b/audio_ptt_win.c
@@ -64,126 +64,110 @@ static unsigned __stdcall ptt_thread ( void *arg );
 
 HANDLE start_ptt_thread (struct audio_s *pa , int ch)
 {
-    save_audio_config_p = pa;
+  save_audio_config_p = pa;
 
-    return (HANDLE)_beginthreadex (NULL, 0, ptt_thread, (void*)(long)ch, 0, NULL);
+  return (HANDLE)_beginthreadex (NULL, 0, ptt_thread, (void*)(long)ch, 0, NULL);
 }
 
 unsigned __stdcall ptt_thread (void *arg)
 {
-    WAVEFORMATEX wf;
-    HWAVEOUT hWaveOut;
-    int ch = (int)(long)arg; // channel number.
-    int channel = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_channel;
-    int freq = save_audio_config_p->achan[channel].octrl[OCTYPE_PTT].ptt_frequency;
-    int a = ACHAN2ADEV( channel );
-    int err;
+  WAVEFORMATEX wf;
+  HWAVEOUT hWaveOut;
+  int ch = (int)(long)arg; // channel number.
+  int channel = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_channel;
+  int freq = save_audio_config_p->achan[channel].octrl[OCTYPE_PTT].ptt_frequency;
+  int a = ACHAN2ADEV( channel );
+  int err;
 
-    if( save_audio_config_p->adev[a].defined ) {
-        wf.wFormatTag = WAVE_FORMAT_PCM;
-        wf.nChannels = save_audio_config_p->adev[a].num_channels;
-        wf.nSamplesPerSec = save_audio_config_p->adev[a].samples_per_sec;
-        wf.wBitsPerSample = save_audio_config_p->adev[a].bits_per_sample;
-        wf.nBlockAlign = ( wf.wBitsPerSample / 8 ) * wf.nChannels;
-        wf.nAvgBytesPerSec = wf.nBlockAlign * wf.nSamplesPerSec;
-        wf.cbSize = 0;
+  if (save_audio_config_p->adev[a].defined) {
+    wf.wFormatTag = WAVE_FORMAT_PCM;
+    wf.nChannels = save_audio_config_p->adev[a].num_channels;
+    wf.nSamplesPerSec = save_audio_config_p->adev[a].samples_per_sec;
+    wf.wBitsPerSample = save_audio_config_p->adev[a].bits_per_sample;
+    wf.nBlockAlign = ( wf.wBitsPerSample / 8 ) * wf.nChannels;
+    wf.nAvgBytesPerSec = wf.nBlockAlign * wf.nSamplesPerSec;
+    wf.cbSize = 0;
 
-          /*
-          * Open the audio output device.
-          * Soundcard is only possibility at this time.
-          */
+   /*
+    * Open the audio output device.
+    * Soundcard is only possibility at this time.
+    */
 
-        err = waveOutOpen ( &hWaveOut, atoi( save_audio_config_p->adev[a].adevice_out ), &wf, (DWORD_PTR)NULL, 0, CALLBACK_NULL );
-        if( err == MMSYSERR_NOERROR ) {
-            WAVEHDR waveHeader;
-            short* pnData;
-            short sample;
-            int nSamples = save_audio_config_p->adev[a].samples_per_sec / freq;
-            int i;
+    err = waveOutOpen ( &hWaveOut, atoi( save_audio_config_p->adev[a].adevice_out ), &wf, (DWORD_PTR)NULL, 0, CALLBACK_NULL );
+    if (err == MMSYSERR_NOERROR) {
+      WAVEHDR waveHeader;
+      short* pnData;
+      short sample;
+      int nSamples = save_audio_config_p->adev[a].samples_per_sec / freq;
+      int i;
+      int j;
 
-            waveHeader.dwBufferLength = save_audio_config_p->adev[a].num_channels * nSamples * sizeof( short );
-            waveHeader.lpData = malloc( waveHeader.dwBufferLength );
-            waveHeader.dwUser = 0;
-            waveHeader.dwFlags = WHDR_BEGINLOOP | WHDR_ENDLOOP;
-            waveHeader.dwLoops = 0xFFFF;
+      waveHeader.dwBufferLength = save_audio_config_p->adev[a].num_channels * nSamples * sizeof( short );
+      waveHeader.lpData = malloc( waveHeader.dwBufferLength );
+      waveHeader.dwUser = 0;
+      waveHeader.dwFlags = WHDR_BEGINLOOP | WHDR_ENDLOOP;
+      waveHeader.dwLoops = 0xFFFF;
 
-            pnData = (short*)waveHeader.lpData;
+      pnData = (short*)waveHeader.lpData;
 
-            if( save_audio_config_p->adev[a].num_channels == 1 ) {
-                for( i = 0; i < nSamples; i++ ) {
-                    sample = (short)( (double)SHRT_MAX * sin( ( (double)i / (double)nSamples ) * 2.0 * M_PI ) );
-                    pnData[i] = sample;
-                }
-            }
-            else {
-                for( i = 0; i < nSamples; i++ ) {
-                    sample = (short)( (double)SHRT_MAX * sin( ( (double)i / (double)nSamples ) * 2.0 * M_PI ) );
-                    if( channel == ADEVFIRSTCHAN( a ) ) {
-
-                        // Stereo, left channel.
-
-                        pnData[i*2 + 0] = sample;
-                        pnData[i*2 + 1] = 0;
-                    }
-                    else {
-
-                        // Stereo, right channel.
-
-                        pnData[i*2 + 0] = 0;
-                        pnData[i*2 + 1] = sample;
-                    }
-                }
-            }
-
-            err = waveOutPrepareHeader ( hWaveOut, &waveHeader, sizeof( WAVEHDR ) );
-            if( err == MMSYSERR_NOERROR ) {
-                HANDLE handles[3];
-                DWORD dwWait;
-
-                handles[0] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_start;
-                handles[1] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_stop;
-                handles[2] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_close;
-
-                while( 1 )
-                {
-                    dwWait = WaitForMultipleObjects ( 3, handles, FALSE, INFINITE );
-
-                    if( dwWait == WAIT_OBJECT_0 + 0 )
-                    {
-                        //
-                        // ptt_set on
-                        //
-
-                        waveOutWrite ( hWaveOut, &waveHeader, sizeof( WAVEHDR ) );
-                    }
-                    else if( dwWait == WAIT_OBJECT_0 + 1 )
-                    {
-                        //
-                        // ptt_set off
-                        //
-
-                        waveOutReset ( hWaveOut );
-                    }
-                    else if( dwWait == WAIT_OBJECT_0 + 2 )
-                    {
-                        //
-                        // close
-                        //
-
-                        waveOutReset ( hWaveOut );
-                        waveOutUnprepareHeader ( hWaveOut, &waveHeader, sizeof( WAVEHDR ) );
-
-                        break;
-                    }
-                }
-            }
-
-            waveOutClose ( hWaveOut );
-
-            free( waveHeader.lpData );
+	    for (i = 0; i < nSamples; i++) {
+        sample = (short)( (double)SHRT_MAX * sin( ( (double)i / (double)nSamples ) * 2.0 * M_PI ) );
+          
+        for (j = 0; j < save_audio_config_p->adev[a].num_channels; j++) {
+	        if (channel == ADEVFIRSTCHAN( a ) + j) {
+            pnData[i*save_audio_config_p->adev[a].num_channels + j] = sample;
+          } else {
+		        pnData[i*save_audio_config_p->adev[a].num_channels + j] = 0;
+          }
         }
-    }
+      }
 
-    return 0;
+      err = waveOutPrepareHeader (hWaveOut, &waveHeader, sizeof( WAVEHDR ));
+      if (err == MMSYSERR_NOERROR) {
+        HANDLE handles[3];
+        DWORD dwWait;
+
+        handles[0] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_start;
+        handles[1] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_stop;
+        handles[2] = save_audio_config_p->achan[ch].octrl[OCTYPE_PTT].ptt_close;
+
+        while (1)
+        {
+          dwWait = WaitForMultipleObjects (3, handles, FALSE, INFINITE);
+
+          if (dwWait == WAIT_OBJECT_0 + 0) {
+            //
+            // ptt_set on
+            //
+
+            waveOutWrite ( hWaveOut, &waveHeader, sizeof( WAVEHDR ) );
+          }
+          else if (dwWait == WAIT_OBJECT_0 + 1) {
+            //
+            // ptt_set off
+            //
+
+            waveOutReset ( hWaveOut );
+          }
+          else if( dwWait == WAIT_OBJECT_0 + 2 ) {
+            //
+            // close
+            //
+
+            waveOutReset ( hWaveOut );
+            waveOutUnprepareHeader ( hWaveOut, &waveHeader, sizeof( WAVEHDR ) );
+
+            break;
+          }
+        }
+      }
+
+      waveOutClose ( hWaveOut );
+
+      free( waveHeader.lpData );
+    }
+  }
+
+  return 0;
 }
 #endif
diff --git a/config.c b/config.c
index e8b828d..363d9de 100644
--- a/config.c
+++ b/config.c
@@ -673,6 +673,7 @@ void config_init (char *fname, struct audio_s *p_audio_config,
         p_audio_config->achan[channel].octrl[ot].ptt_stop = NULL;
         p_audio_config->achan[channel].octrl[ot].ptt_close = NULL;
 #else
+        p_audio_config->achan[channel].octrl[ot].ptt_state = PTT_AUDIO_STATE_STOP;
 #endif
       }
 
@@ -1635,6 +1636,9 @@ void config_init (char *fname, struct audio_s *p_audio_config,
           p_audio_config->achan[channel].octrl[ot].ptt_stop = CreateEvent (NULL, FALSE, FALSE, NULL);
           p_audio_config->achan[channel].octrl[ot].ptt_close = CreateEvent (NULL, FALSE, FALSE, NULL);
 #else
+          p_audio_config->achan[channel].octrl[ot].ptt_state = PTT_AUDIO_STATE_STOP;
+          pthread_mutex_init(&p_audio_config->achan[channel].octrl[ot].ptt_mutex, 0);
+          pthread_cond_init(&p_audio_config->achan[channel].octrl[ot].ptt_condition, 0);
 #endif
         }
         else  {
diff --git a/ptt.c b/ptt.c
index 1b2e34c..bec7a97 100644
--- a/ptt.c
+++ b/ptt.c
@@ -1010,22 +1010,27 @@ void ptt_set (int ot, int chan, int ptt_signal)
     * Using audio channel?
     */
 
-    if( save_audio_config_p->achan[chan].octrl[ot].ptt_method == PTT_METHOD_AUDIO ) {
-        if( ptt_signal ) {
+    if (save_audio_config_p->achan[chan].octrl[ot].ptt_method == PTT_METHOD_AUDIO) {
+      if (ptt_signal) {
 #ifdef __WIN32__
-            SetEvent( save_audio_config_p->achan[chan].octrl[ot].ptt_start );
+        SetEvent (save_audio_config_p->achan[chan].octrl[ot].ptt_start);
 #else
-
+        pthread_mutex_lock (&save_audio_config_p->achan[chan].octrl[ot].ptt_mutex);
+        save_audio_config_p->achan[chan].octrl[ot].ptt_state = PTT_AUDIO_STATE_START;
+        pthread_cond_signal (&save_audio_config_p->achan[chan].octrl[ot].ptt_condition);
+        pthread_mutex_unlock (&save_audio_config_p->achan[chan].octrl[ot].ptt_mutex);
 #endif
-        }
-        else
-        {
+      }
+      else
+      {
 #ifdef __WIN32__
-            SetEvent( save_audio_config_p->achan[chan].octrl[ot].ptt_stop );
+        SetEvent (save_audio_config_p->achan[chan].octrl[ot].ptt_stop);
 #else
-
+        pthread_mutex_lock (&save_audio_config_p->achan[chan].octrl[ot].ptt_mutex);
+        save_audio_config_p->achan[chan].octrl[ot].ptt_state = PTT_AUDIO_STATE_STOP;
+        pthread_mutex_unlock (&save_audio_config_p->achan[chan].octrl[ot].ptt_mutex);
 #endif
-        }
+      }
     }
 } /* end ptt_set */
 
@@ -1137,7 +1142,10 @@ void ptt_term (void)
 #ifdef __WIN32__
         SetEvent (save_audio_config_p->achan[n].octrl[OCTYPE_PTT].ptt_close) ;
 #else
-
+        pthread_mutex_lock (&save_audio_config_p->achan[n].octrl[OCTYPE_PTT].ptt_mutex);
+        save_audio_config_p->achan[n].octrl[OCTYPE_PTT].ptt_state = PTT_AUDIO_STATE_CLOSE;
+        pthread_cond_signal (&save_audio_config_p->achan[n].octrl[OCTYPE_PTT].ptt_condition);
+        pthread_mutex_unlock (&save_audio_config_p->achan[n].octrl[OCTYPE_PTT].ptt_mutex);
 #endif
       }
     }