diff --git a/MotorDriver.cpp b/MotorDriver.cpp
index 5420488..ae832e9 100644
--- a/MotorDriver.cpp
+++ b/MotorDriver.cpp
@@ -34,19 +34,20 @@
     #define ReadPin digitalRead2
 #endif
     
-MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, byte brake_pin, 
+MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin,
                          byte current_pin, float sense_factor, unsigned int trip_milliamps, byte fault_pin) {
-   powerPin=power_pin;
-   signalPin=signal_pin;
-   signalPin2=signal_pin2;
-   brakePin=brake_pin;
-   currentPin=current_pin;
-   senseFactor=sense_factor;
-   faultPin=fault_pin;
-   tripMilliamps=trip_milliamps;
-   rawCurrentTripValue=(int)(trip_milliamps / sense_factor);
+  powerPin=power_pin;
+  signalPin=signal_pin;
+  signalPin2=signal_pin2;
+  brakePin=brake_pin;
+  currentPin=current_pin;
+  senseFactor=sense_factor;
+  faultPin=fault_pin;
+  tripMilliamps=trip_milliamps;
+  rawCurrentTripValue=(int)(trip_milliamps / sense_factor);
   pinMode(powerPin, OUTPUT);
-  pinMode(brakePin, OUTPUT);
+  pinMode(brakePin < 0 ? -brakePin : brakePin, OUTPUT);
+  setBrake(false);
   pinMode(signalPin, OUTPUT);
   if (signalPin2 != UNUSED_PIN) pinMode(signalPin2, OUTPUT);
   pinMode(currentPin, INPUT);
@@ -54,10 +55,32 @@ MotorDriver::MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, byte
 }
 
 void MotorDriver::setPower(bool on) {
+  if (brakePin == -4 && on) {
+    // toggle brake before turning power on - resets overcurrent error
+    // on the Pololu board if brake is wired to ^D2.
+    setBrake(true);
+    setBrake(false);
+  }
   WritePin(powerPin, on ? HIGH : LOW);
 }
-void MotorDriver::setBrake( bool on) {
-  WritePin(brakePin, on ? HIGH : LOW);
+
+// setBrake applies brake if on == true. So to get
+// voltage from the motor bride one needs to do a
+// setBrake(false).
+// If the brakePin is negative that means the sense
+// of the brake pin on the motor bridge is inverted
+// (HIGH == release brake) and setBrake does
+// compensate for that.
+//
+void MotorDriver::setBrake(bool on) {
+    bool state = on;
+    byte pin = brakePin;
+    if (brakePin < 0) {
+      pin=-pin;
+      state=!state;
+    }
+    WritePin(pin, state ? HIGH : LOW);
+    //DIAG(F("BrakePin: %d is %d\n"), pin, ReadPin(pin));
 }
 
 void MotorDriver::setSignal( bool high) {
diff --git a/MotorDriver.h b/MotorDriver.h
index cbc09cc..3f67080 100644
--- a/MotorDriver.h
+++ b/MotorDriver.h
@@ -20,9 +20,13 @@
 #define MotorDriver_h
 // Virtualised Motor shield 1-track hardware Interface
 
+#ifndef UNUSED_PIN     // sync define with the one in MotorDrivers.h
+#define UNUSED_PIN 127 // inside int8_t
+#endif
+
 class MotorDriver {
   public:
-    MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, byte brake_pin, byte current_pin, float senseFactor, unsigned int tripMilliamps, byte faultPin);
+    MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin, byte current_pin, float senseFactor, unsigned int tripMilliamps, byte faultPin);
     virtual void setPower( bool on);
     virtual void setSignal( bool high);
     virtual void setBrake( bool on);
@@ -34,11 +38,10 @@ class MotorDriver {
     }
 
   private:
-    byte powerPin, signalPin, signalPin2, brakePin,currentPin,faultPin;
+    byte powerPin, signalPin, signalPin2, currentPin, faultPin;
+    int8_t brakePin;       // negative means pin is inverted
     float senseFactor;
     unsigned int tripMilliamps;
     int rawCurrentTripValue;
-    const byte UNUSED_PIN = 255;
-    
 };
 #endif
diff --git a/MotorDrivers.h b/MotorDrivers.h
index 3695e0a..ef1e2cf 100644
--- a/MotorDrivers.h
+++ b/MotorDrivers.h
@@ -13,10 +13,16 @@
 // similar to those defined here, WITHOUT editing this file. You can put your
 // custom defines in config.h.
 
-const byte UNUSED_PIN = 255;
+#ifndef UNUSED_PIN     // sync define with the one in MotorDriver.h
+#define UNUSED_PIN 127 // inside int8_t
+#endif
 
-// MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, byte brake_pin, byte current_pin,
+// MotorDriver(byte power_pin, byte signal_pin, byte signal_pin2, int8_t brake_pin, byte current_pin,
 //             float senseFactor, unsigned int tripMilliamps, byte faultPin);
+//
+// If the brakePin is negative that means the sense
+// of the brake pin on the motor bridge is inverted
+// (HIGH == release brake)
 
 // Arduino standard Motor Shield
 #define STANDARD_MOTOR_SHIELD F("STANDARD_MOTOR_SHIELD"),                                                 \
@@ -24,9 +30,19 @@ const byte UNUSED_PIN = 255;
                               new MotorDriver(11, 13, UNUSED_PIN, UNUSED_PIN, A1, 2.99, 2000, UNUSED_PIN)
 
 // Pololu Motor Shield
-#define POLOLU_MOTOR_SHIELD F("POLOLU_MOTOR_SHIELD"),                               \
-                            new MotorDriver(4, 7, UNUSED_PIN, 9, A0, 18, 3000, 12), \
-                            new MotorDriver(2, 8, UNUSED_PIN, 10, A1, 18, 3000, UNUSED_PIN)
+#define POLOLU_MOTOR_SHIELD F("POLOLU_MOTOR_SHIELD"),                                                 \
+                            new MotorDriver( 9, 7, UNUSED_PIN,         -4, A0, 18, 3000,         12), \
+                            new MotorDriver(10, 8, UNUSED_PIN, UNUSED_PIN, A1, 18, 3000, UNUSED_PIN)
+//
+// Actually, on the Pololu MC33926 shield the enable lines are tied together on pin 4 and the
+// pins 9 and 10 work as "inverted brake" but as we turn on and off the tracks individually
+// via the power pins we above use 9 and 10 as power pins and 4 as "inverted brake" which in this
+// version of the code always will be high. That means this config is not usable for generating
+// a railcom cuotout in the future. For that one must wire the second ^D2 to pin 2 and define
+// the motor driver like this:
+//                          new MotorDriver(4, 7, UNUSED_PIN,  -9, A0, 18, 3000,         12)
+//                          new MotorDriver(2, 8, UNUSED_PIN, -10, A1, 18, 3000, UNUSED_PIN)
+// See Pololu dial_mc33926_shield_schematic.pdf and truth table on page 17 of the MC33926 data sheet.
 
 // Firebox Mk1
 #define FIREBOX_MK1 F("FIREBOX_MK1"),                                                  \