diff --git a/CMS_CORE_Library/S7Net/Nc_S7Net.cs b/CMS_CORE_Library/S7Net/Nc_S7Net.cs
index 7d2fa76..f49500c 100644
--- a/CMS_CORE_Library/S7Net/Nc_S7Net.cs
+++ b/CMS_CORE_Library/S7Net/Nc_S7Net.cs
@@ -69,6 +69,10 @@ namespace CMS_CORE_Library.S7Net
         /// Oggetto PLC da ri-utilizzare...
         /// </summary>
         protected Plc currPLC;
+        /// <summary>
+        /// Lock per connessione PLC
+        /// </summary>
+        private readonly object connectLock = new object();
 
         #endregion
 
@@ -137,40 +141,42 @@ namespace CMS_CORE_Library.S7Net
         /// <returns></returns>
         public override CmsError NC_Connect()
         {
-            // Try to get information
-            try
+            lock (connectLock)
             {
-                // Check if Siemens Environment is started
-                CmsError libraryError = CheckS7Ping();
-                if (libraryError.IsError())
-                    return libraryError;
-
-                // Check connection
-                currPLC = new Plc(tipoCpu, this.Ip, this.rack, this.slot);
-                currPLC.Open();
-                if (currPLC.IsConnected)
-                    Connected = true;
-
-                // FARE TODO FIXME
-                // Setup the alarms (with DB bitmap) --> PlcMessages
-
-                if (this.EnableAlarms)
+                // Try to get information
+                try
                 {
-                    // PlcMessages
+                    // Check if Siemens Environment is started
+                    CmsError libraryError = CheckS7Ping();
+                    if (libraryError.IsError())
+                        return libraryError;
+
+                    // Check connection
+                    currPLC = new Plc(tipoCpu, this.Ip, this.rack, this.slot);
+                    currPLC.Open();
+                    if (currPLC.IsConnected)
+                        Connected = true;
+
+                    // FARE TODO FIXME
+                    // Setup the alarms (with DB bitmap) --> PlcMessages
+
+                    if (this.EnableAlarms)
+                    {
+                        // PlcMessages
 #if false
                     SiemensAlarms = new Alarm[] { };
                     SiemensAlmSvc = new AlarmSvc(ConvertToSTEPLanguage(SiemensLanguage).ThreeLetterISOLanguageName);
                     SiemensAlmSvc.Subscribe(AlarmsChanged);
                     Infrastructure.SubscribeLanguageChanged(NcLanguageChanged); 
 #endif
+                    }
+
+                }
+                catch (Exception ex)
+                {
+                    return ManageException(ex);
                 }
-
             }
-            catch (Exception ex)
-            {
-                return ManageException(ex);
-            }
-
             return NO_ERROR;
         }
         /// <summary>