diff --git a/DCCPacket.h b/DCCPacket.h
index 261cff3..9ac480a 100644
--- a/DCCPacket.h
+++ b/DCCPacket.h
@@ -2,6 +2,10 @@
 
 const byte MAX_PACKET_SIZE = 5;  // NMRA standard extended packets, payload size WITHOUT checksum.
 
+// Number of preamble bits (moved here so MotorDriver and Waveform know)
+const int   PREAMBLE_BITS_MAIN = 16;
+const int   PREAMBLE_BITS_PROG = 22;
+
 class dccPacket {
  public:
   byte data[MAX_PACKET_SIZE+1]; // space for checksum if needed
diff --git a/DCCRMT.cpp b/DCCRMT.cpp
index 6a81c25..e26dd18 100644
--- a/DCCRMT.cpp
+++ b/DCCRMT.cpp
@@ -62,7 +62,7 @@ void IRAM_ATTR interrupt(rmt_channel_t channel, void *t) {
   tt->RMTinterrupt();
 }
 
-RMTChannel::RMTChannel(byte pin, byte ch, byte plen) {
+RMTChannel::RMTChannel(byte pin, byte ch, byte plen, bool isMain) {
 
   // preamble
   preambleLen = plen+2; // plen 1 bits, one 0 bit and one EOF marker
@@ -79,12 +79,17 @@ RMTChannel::RMTChannel(byte pin, byte ch, byte plen) {
   // idle
   idleLen = 28;
   idle = (rmt_item32_t*)malloc(idleLen*sizeof(rmt_item32_t));
-  for (byte n=0; n<8; n++)   // 0 to 7
-    setDCCBit1(idle + n);
-  for (byte n=8; n<18; n++)  // 8, 9 to 16, 17
-    setDCCBit0(idle + n);
-  for (byte n=18; n<26; n++) // 18 to 25
-    setDCCBit1(idle + n);
+  if (isMain) {
+    for (byte n=0; n<8; n++)   // 0 to 7
+      setDCCBit1(idle + n);
+    for (byte n=8; n<18; n++)  // 8, 9 to 16, 17
+      setDCCBit0(idle + n);
+    for (byte n=18; n<26; n++) // 18 to 25
+      setDCCBit1(idle + n);
+  } else {
+    for (byte n=0; n<26; n++)  // all zero
+      setDCCBit0(idle + n);
+  }
   setDCCBit1(idle + 26);     // end bit
   setEOT(idle + 27);         // EOT marker
 
diff --git a/DCCRMT.h b/DCCRMT.h
index 8d8a93c..94234e7 100644
--- a/DCCRMT.h
+++ b/DCCRMT.h
@@ -32,7 +32,13 @@
 
 class RMTChannel {
  public:
-  RMTChannel(byte pin, byte ch, byte plen);
+  inline RMTChannel(byte pin, bool isMain) {
+    if (isMain)
+      RMTChannel(pin, 0, PREAMBLE_BITS_MAIN, 1);
+    else
+      RMTChannel(pin, 2, PREAMBLE_BITS_PROG, 0);
+  };
+  RMTChannel(byte pin, byte ch, byte plen, bool isProg);
   void IRAM_ATTR RMTinterrupt();
   void RMTprefill();
   bool RMTfillData(dccPacket packet);
diff --git a/MotorDriver.cpp b/MotorDriver.cpp
index ee878ec..5f3d68a 100644
--- a/MotorDriver.cpp
+++ b/MotorDriver.cpp
@@ -41,7 +41,7 @@ MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8
   if (dtype == RMT_MAIN) {
     signalPin=signal_pin;
 #if defined(ARDUINO_ARCH_ESP32)
-    rmtChannel = new RMTChannel(signalPin, 0, PREAMBLE_BITS_MAIN);
+    rmtChannel = new RMTChannel(signalPin, true); // true: isMain
 #endif
     dualSignal=false;
   } else if (dtype & (TIMER_MAIN | TIMER_PROG)) {
diff --git a/MotorDriver.h b/MotorDriver.h
index da9e0d9..65f97f2 100644
--- a/MotorDriver.h
+++ b/MotorDriver.h
@@ -29,10 +29,6 @@
 #include "DCCRMT.h"
 #endif
 
-// Number of preamble bits (moved here so MotorDriver and Waveform know)
-const int   PREAMBLE_BITS_MAIN = 16;
-const int   PREAMBLE_BITS_PROG = 22;
-
 #ifndef UNUSED_PIN     // sync define with the one in MotorDrivers.h
 #define UNUSED_PIN 127 // inside int8_t
 #endif