diff --git a/Config.h b/Config.h
index 7426ef3..bfa4225 100644
--- a/Config.h
+++ b/Config.h
@@ -1,3 +1,6 @@
+#ifndef Config_h
+#define Config_h
+
 // This hardware configuration would normally be setup using a bunch of #ifdefs.
 
 const byte MAIN_POWER_PIN = 3;
@@ -14,3 +17,10 @@ const byte PROG_SENSE_PIN = A1;
 const byte PROG_BRAKE_PIN = 10;
 
 const float PROG_SENSE_FACTOR=1; //  analgRead(PROG_SENSE_PIN) * PROG_SENSE_FACTOR = milliamps 
+
+// Allocations with memory implications.. however tiny!
+// Base system takes approx 500 bytes + 4 per loco and 3 per turnout.
+const byte MAX_LOCOS=50;             
+const byte MAX_TURNOUTS=50;
+
+#endif
diff --git a/DCC.cpp b/DCC.cpp
index 96fa0cb..cd8f635 100644
--- a/DCC.cpp
+++ b/DCC.cpp
@@ -1,6 +1,7 @@
 #include "DCC.h"
 #include "DCCWaveform.h"
 #include "DIAG.h"
+
 // This module is responsible for converting API calls into
 // messages to be sent to the waveform generator.
 // It has no visibility of the hardware, timers, interrupts
diff --git a/DCC.h b/DCC.h
index 3858eca..8022454 100644
--- a/DCC.h
+++ b/DCC.h
@@ -1,5 +1,8 @@
+#ifndef DCC_h
+#define DCC_h
 #include <Arduino.h>
-const byte MAX_LOCOS=50;
+#include "Config.h"
+
 
 class DCC {
   public:
@@ -34,3 +37,4 @@ private:
   static byte cv2(int cv);
   
 };
+#endif
diff --git a/DCCWaveform.h b/DCCWaveform.h
index 6a83741..9cfca89 100644
--- a/DCCWaveform.h
+++ b/DCCWaveform.h
@@ -1,4 +1,5 @@
-
+#ifndef DCCWaveform_h
+#define DCCWaveform_h
 
 
 const int  POWER_SAMPLE_MAX = 300;
@@ -77,3 +78,4 @@ class DCCWaveform {
     POWERMODE powerMode;
     unsigned long nextSampleDue;
 };
+#endif
diff --git a/DIAG.h b/DIAG.h
index 76526a5..8a75b62 100644
--- a/DIAG.h
+++ b/DIAG.h
@@ -1,5 +1,9 @@
+#ifndef DIAG_h
+#define DIAG_h
+
 #include "StringParser.h"
 #ifndef DIAG_ENABLED
  #define DIAG_ENABLED true
 #endif
 #define DIAG if (DIAG_ENABLED) StringParser::print
+#endif
diff --git a/Hardware.h b/Hardware.h
index 8709f4e..7b68466 100644
--- a/Hardware.h
+++ b/Hardware.h
@@ -1,4 +1,5 @@
-
+#ifndef Hardware_h
+#define Hardware_h
 // Virtualised hardware Interface
 class Hardware {
   public:
@@ -11,3 +12,4 @@ class Hardware {
     static void setSingleCallback(int duration,  void (*isr)());
     static void resetSingleCallback(int duration);
 };
+#endif
diff --git a/JMRIParser.h b/JMRIParser.h
index b1b7dc0..6660d4c 100644
--- a/JMRIParser.h
+++ b/JMRIParser.h
@@ -1,4 +1,5 @@
-
+#ifndef JMRIParser_h
+#define JMRIParser_h
 struct JMRIParser
 {
     static void parse(Stream & stream,const char * command);
@@ -7,3 +8,4 @@ struct JMRIParser
     static const int MAX_PARAMS=10; 
     static int p[MAX_PARAMS];
 };
+#endif
diff --git a/JMRITurnout.cpp b/JMRITurnout.cpp
index 5c6514b..f4d6cad 100644
--- a/JMRITurnout.cpp
+++ b/JMRITurnout.cpp
@@ -91,7 +91,7 @@ void JMRITurnout::parse(Stream & stream, int params, int p[]) {
 }
 
 ///////////////// ALL PRIVATE BELOW HERE //////////////////
- JMRITurnout::TurnoutEntry JMRITurnout::table[JMRITurnout::MAX_TURNOUTS];
+ JMRITurnout::TurnoutEntry JMRITurnout::table[MAX_TURNOUTS];
 
  bool JMRITurnout::create(int id, int add, byte subAdd){
   if (id<0 || id>=MAX_TURNOUTS || table[id].address!=0) return false;
diff --git a/JMRITurnout.h b/JMRITurnout.h
index a14ab3a..75847c0 100644
--- a/JMRITurnout.h
+++ b/JMRITurnout.h
@@ -1,4 +1,8 @@
+#ifndef JMRITurnout_h
+#define TMRITurnout_h
+
 #include <Arduino.h>
+#include "Config.h"
 
 class JMRITurnout {
 
@@ -21,6 +25,6 @@ class JMRITurnout {
          byte subAddress;
          bool thrown;
   };
-  static const int MAX_TURNOUTS=50;
   static TurnoutEntry table[MAX_TURNOUTS];
 };
+#endif
diff --git a/Railcom.h b/Railcom.h
index aa85c6b..08dafd0 100644
--- a/Railcom.h
+++ b/Railcom.h
@@ -1,3 +1,6 @@
+#ifndef Railcom_h
+#define Railcom_h
+
 #include <Arduino.h>
 class Railcom {
   public:
@@ -9,3 +12,5 @@ class Railcom {
     static const byte MAX_BUFFER=20;
     static byte buffer[MAX_BUFFER];    
 };
+
+#endif
diff --git a/StringParser.h b/StringParser.h
index e1ec581..1d11bca 100644
--- a/StringParser.h
+++ b/StringParser.h
@@ -1,3 +1,5 @@
+#ifndef StringParser_h
+#define StringParser_h
 #include <Arduino.h>
 class StringParser
 {
@@ -14,3 +16,4 @@ class StringParser
     static const byte MAX_BUFFER=100;
     static char buffer[MAX_BUFFER];
 };
+#endif