diff --git a/DCCEXParser.cpp b/DCCEXParser.cpp
index 60b2233..9fb2b29 100644
--- a/DCCEXParser.cpp
+++ b/DCCEXParser.cpp
@@ -43,7 +43,8 @@ const int HASH_KEYWORD_WIT=31594;
 const int HASH_KEYWORD_WIFI=-5583;
 const int HASH_KEYWORD_ACK=3113;
 const int HASH_KEYWORD_ON=2657;
-const int HASH_KEYWORD_OFF=22479;
+const int HASH_KEYWORD_DCC=6436;
+const int HASH_KEYWORD_SLOW=-17209;
 
 
 int DCCEXParser::stashP[MAX_PARAMS];
@@ -455,7 +456,7 @@ bool DCCEXParser::parseS( Print * stream,int params, int p[]) {
 
 bool DCCEXParser::parseD( Print * stream,int params, int p[]) {
     if (params==0) return false;
-    bool onOff=p[1]==1 || p[1]==HASH_KEYWORD_ON; // dont care if other stuff or missing... just means off 
+    bool onOff=(params>0) && (p[1]==1 || p[1]==HASH_KEYWORD_ON); // dont care if other stuff or missing... just means off 
     switch(p[0]){
         case HASH_KEYWORD_CABS:                     // <D CABS>
             DCC::displayCabList(stream);
@@ -481,6 +482,9 @@ bool DCCEXParser::parseD( Print * stream,int params, int p[]) {
             Diag::WITHROTTLE=onOff;      
             return true;
 
+        case HASH_KEYWORD_DCC:
+            DCCWaveform::setDiagnosticSlowWave(params>=1 && p[1]==HASH_KEYWORD_SLOW);
+            return true;
         default:                     // invalid/unknown 
             break;
         }
diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index 2a59852..67203aa 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -22,6 +22,8 @@
 #include "DCCWaveform.h"
 #include "DIAG.h"
  
+const int NORMAL_SIGNAL_TIME=58;  // this is the 58uS DCC 1-bit waveform half-cycle 
+const int SLOW_SIGNAL_TIME=NORMAL_SIGNAL_TIME*256;
 
 DCCWaveform  DCCWaveform::mainTrack(PREAMBLE_BITS_MAIN, true);
 DCCWaveform  DCCWaveform::progTrack(PREAMBLE_BITS_PROG, false);
@@ -47,10 +49,15 @@ void DCCWaveform::begin(MotorDriver * mainDriver, MotorDriver * progDriver, byte
       return;
   }
   interruptTimer->initialize();
-  interruptTimer->setPeriod(58); // this is the 58uS DCC 1-bit waveform half-cycle
+  interruptTimer->setPeriod(NORMAL_SIGNAL_TIME); // this is the 58uS DCC 1-bit waveform half-cycle
   interruptTimer->attachInterrupt(interruptHandler);
   interruptTimer->start();
 }
+void DCCWaveform::setDiagnosticSlowWave(bool slow) {
+  interruptTimer->setPeriod(slow? SLOW_SIGNAL_TIME : NORMAL_SIGNAL_TIME);
+  interruptTimer->start(); 
+  DIAG(F("\nDCC SLOW WAVE %S\n"),slow?F("SET. DO NOT ADD LOCOS TO TRACK"):F("RESET")); 
+}
 
 void DCCWaveform::loop() {
   mainTrack.checkPowerOverload();
diff --git a/DCCWaveform.h b/DCCWaveform.h
index fa2d444..96e5887 100644
--- a/DCCWaveform.h
+++ b/DCCWaveform.h
@@ -49,6 +49,7 @@ class DCCWaveform {
   public:
     DCCWaveform( byte preambleBits, bool isMain);
     static void begin(MotorDriver * mainDriver, MotorDriver * progDriver, byte timerNumber);
+    static void setDiagnosticSlowWave(bool slow);
     static void loop();
     static DCCWaveform  mainTrack;
     static DCCWaveform  progTrack;