diff --git a/wpilibc/sim/src/Relay.cpp b/wpilibc/sim/src/Relay.cpp
new file mode 100644
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--- /dev/null
+++ b/wpilibc/sim/src/Relay.cpp
@@ -0,0 +1,245 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2008-2017. All Rights Reserved.                        */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "Relay.h"
+
+#include <sstream>
+
+#include "LiveWindow/LiveWindow.h"
+#include "MotorSafetyHelper.h"
+#include "WPIErrors.h"
+
+using namespace frc;
+
+/**
+ * Relay constructor given a channel.
+ *
+ * This code initializes the relay and reserves all resources that need to be
+ * locked. Initially the relay is set to both lines at 0v.
+ *
+ * @param channel   The channel number (0-3).
+ * @param direction The direction that the Relay object will control.
+ */
+Relay::Relay(int channel, Relay::Direction direction)
+    : m_channel(channel), m_direction(direction) {
+  std::stringstream ss;
+  if (!SensorBase::CheckRelayChannel(m_channel)) {
+    ss << "Relay Channel " << m_channel;
+    wpi_setWPIErrorWithContext(ChannelIndexOutOfRange, ss.str());
+    return;
+  }
+
+  m_safetyHelper = std::make_unique<MotorSafetyHelper>(this);
+  m_safetyHelper->SetSafetyEnabled(false);
+
+  ss << "relay/" << m_channel;
+  impl = new SimContinuousOutput(ss.str());  // TODO: Allow two different relays
+                                             // (targetting the different halves
+                                             // of a relay) to be combined to
+                                             // control one motor.
+  LiveWindow::GetInstance()->AddActuator("Relay", 1, m_channel, this);
+  go_pos = go_neg = false;
+}
+
+/**
+ * Free the resource associated with a relay.
+ *
+ * The relay channels are set to free and the relay output is turned off.
+ */
+Relay::~Relay() {
+  impl->Set(0);
+  if (m_table != nullptr) m_table->RemoveTableListener(this);
+}
+
+/**
+ * Set the relay state.
+ *
+ * Valid values depend on which directions of the relay are controlled by the
+ * object.
+ *
+ * When set to kBothDirections, the relay can be any of the four states:
+ *    0v-0v, 0v-12v, 12v-0v, 12v-12v
+ *
+ * When set to kForwardOnly or kReverseOnly, you can specify the constant for
+ * the direction or you can simply specify kOff and kOn.  Using only kOff and
+ * kOn is recommended.
+ *
+ * @param value The state to set the relay.
+ */
+void Relay::Set(Relay::Value value) {
+  switch (value) {
+    case kOff:
+      if (m_direction == kBothDirections || m_direction == kForwardOnly) {
+        go_pos = false;
+      }
+      if (m_direction == kBothDirections || m_direction == kReverseOnly) {
+        go_neg = false;
+      }
+      break;
+    case kOn:
+      if (m_direction == kBothDirections || m_direction == kForwardOnly) {
+        go_pos = true;
+      }
+      if (m_direction == kBothDirections || m_direction == kReverseOnly) {
+        go_neg = true;
+      }
+      break;
+    case kForward:
+      if (m_direction == kReverseOnly) {
+        wpi_setWPIError(IncompatibleMode);
+        break;
+      }
+      if (m_direction == kBothDirections || m_direction == kForwardOnly) {
+        go_pos = true;
+      }
+      if (m_direction == kBothDirections) {
+        go_neg = false;
+      }
+      break;
+    case kReverse:
+      if (m_direction == kForwardOnly) {
+        wpi_setWPIError(IncompatibleMode);
+        break;
+      }
+      if (m_direction == kBothDirections) {
+        go_pos = false;
+      }
+      if (m_direction == kBothDirections || m_direction == kReverseOnly) {
+        go_neg = true;
+      }
+      break;
+  }
+  impl->Set((go_pos ? 1 : 0) + (go_neg ? -1 : 0));
+}
+
+/**
+ * Get the Relay State
+ *
+ * Gets the current state of the relay.
+ *
+ * When set to kForwardOnly or kReverseOnly, value is returned as kOn/kOff not
+ * kForward/kReverse (per the recommendation in Set).
+ *
+ * @return The current state of the relay as a Relay::Value
+ */
+Relay::Value Relay::Get() const {
+  // TODO: Don't assume that the go_pos and go_neg fields are correct?
+  if ((go_pos || m_direction == kReverseOnly) &&
+      (go_neg || m_direction == kForwardOnly)) {
+    return kOn;
+  } else if (go_pos) {
+    return kForward;
+  } else if (go_neg) {
+    return kReverse;
+  } else {
+    return kOff;
+  }
+}
+
+int Relay::GetChannel() const { return m_channel; }
+
+/**
+ * Set the expiration time for the Relay object.
+ *
+ * @param timeout The timeout (in seconds) for this relay object
+ */
+void Relay::SetExpiration(double timeout) {
+  m_safetyHelper->SetExpiration(timeout);
+}
+
+/**
+ * Return the expiration time for the relay object.
+ *
+ * @return The expiration time value.
+ */
+double Relay::GetExpiration() const { return m_safetyHelper->GetExpiration(); }
+
+/**
+ * Check if the relay object is currently alive or stopped due to a timeout.
+ *
+ * @return a bool value that is true if the motor has NOT timed out and should
+ *         still be running.
+ */
+bool Relay::IsAlive() const { return m_safetyHelper->IsAlive(); }
+
+/**
+ * Stop the motor associated with this PWM object.
+ *
+ * This is called by the MotorSafetyHelper object when it has a timeout for this
+ * relay and needs to stop it from running.
+ */
+void Relay::StopMotor() { Set(kOff); }
+
+/**
+ * Enable/disable motor safety for this device
+ *
+ * Turn on and off the motor safety option for this relay object.
+ *
+ * @param enabled True if motor safety is enforced for this object
+ */
+void Relay::SetSafetyEnabled(bool enabled) {
+  m_safetyHelper->SetSafetyEnabled(enabled);
+}
+
+/**
+ * Check if motor safety is enabled for this object.
+ *
+ * @return True if motor safety is enforced for this object
+ */
+bool Relay::IsSafetyEnabled() const {
+  return m_safetyHelper->IsSafetyEnabled();
+}
+
+void Relay::GetDescription(std::ostringstream& desc) const {
+  desc << "Relay " << GetChannel();
+}
+
+void Relay::ValueChanged(ITable* source, llvm::StringRef key,
+                         std::shared_ptr<nt::Value> value, bool isNew) {
+  if (!value->IsString()) return;
+  if (value->GetString() == "Off")
+    Set(kOff);
+  else if (value->GetString() == "Forward")
+    Set(kForward);
+  else if (value->GetString() == "Reverse")
+    Set(kReverse);
+}
+
+void Relay::UpdateTable() {
+  if (m_table != nullptr) {
+    if (Get() == kOn) {
+      m_table->PutString("Value", "On");
+    } else if (Get() == kForward) {
+      m_table->PutString("Value", "Forward");
+    } else if (Get() == kReverse) {
+      m_table->PutString("Value", "Reverse");
+    } else {
+      m_table->PutString("Value", "Off");
+    }
+  }
+}
+
+void Relay::StartLiveWindowMode() {
+  if (m_table != nullptr) {
+    m_table->AddTableListener("Value", this, true);
+  }
+}
+
+void Relay::StopLiveWindowMode() {
+  if (m_table != nullptr) {
+    m_table->RemoveTableListener(this);
+  }
+}
+
+std::string Relay::GetSmartDashboardType() const { return "Relay"; }
+
+void Relay::InitTable(std::shared_ptr<ITable> subTable) {
+  m_table = subTable;
+  UpdateTable();
+}
+
+std::shared_ptr<ITable> Relay::GetTable() const { return m_table; }