diff --git a/res/values/config.xml b/res/values/config.xml
index d4e4c79..423236d 100644
--- a/res/values/config.xml
+++ b/res/values/config.xml
@@ -257,6 +257,16 @@
          audio stream which the remote party will be able to hear. -->
     <bool name="config_support_telephony_audio_device">false</bool>
 
+    <!-- Whether the device supports dialing emergency RTT calls when there's no SIM card installed
+    -->
+    <bool name="config_support_simless_emergency_rtt">false</bool>
+
+    <!-- Array of countries that support sim-less emergency RTT calls. Values should be
+         ISO3166 country codes in lowercase. -->
+    <string-array name="config_simless_emergency_rtt_supported_countries">
+        <item>us</item>
+    </string-array>
+
     <string-array translatable="false" name="config_volte_provision_error_on_publish_response">
         <item>403 not authorized for presence</item>
     </string-array>
diff --git a/src/com/android/phone/settings/AccessibilitySettingsFragment.java b/src/com/android/phone/settings/AccessibilitySettingsFragment.java
index e31de64..37212cf 100644
--- a/src/com/android/phone/settings/AccessibilitySettingsFragment.java
+++ b/src/com/android/phone/settings/AccessibilitySettingsFragment.java
@@ -25,6 +25,7 @@
 import android.preference.PreferenceScreen;
 import android.preference.SwitchPreference;
 import android.provider.Settings;
+import android.telephony.AccessNetworkConstants;
 import android.telephony.CarrierConfigManager;
 import android.telephony.PhoneStateListener;
 import android.telephony.SubscriptionManager;
@@ -39,6 +40,11 @@
 import com.android.phone.PhoneGlobals;
 import com.android.phone.R;
 
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
 public class AccessibilitySettingsFragment extends PreferenceFragment {
     private static final String LOG_TAG = AccessibilitySettingsFragment.class.getSimpleName();
     private static final boolean DBG = (PhoneGlobals.DBG_LEVEL >= 2);
@@ -48,6 +54,8 @@
     private static final String BUTTON_RTT_KEY = "button_rtt_key";
     private static final String RTT_INFO_PREF = "button_rtt_more_information_key";
 
+    private static final int WFC_QUERY_TIMEOUT_MILLIS = 20;
+
     private final PhoneStateListener mPhoneStateListener = new PhoneStateListener() {
         /**
          * Disable the TTY setting when in/out of a call (and if carrier doesn't
@@ -110,10 +118,13 @@
         }
 
         if (shouldShowRttSetting()) {
-            // TODO: this is going to be a on/off switch for now. Ask UX about how to integrate
-            // this settings with TTY
-            if (TelephonyManager.getDefault().isNetworkRoaming(
-                    SubscriptionManager.getDefaultVoiceSubscriptionId())) {
+            TelephonyManager tm =
+                    (TelephonyManager) mContext.getSystemService(Context.TELEPHONY_SERVICE);
+            boolean isRoaming = tm.isNetworkRoaming(
+                    SubscriptionManager.getDefaultVoiceSubscriptionId());
+
+            boolean shouldDisableBecauseRoamingOffWfc = isRoaming && !isOnWfc();
+            if (shouldDisableBecauseRoamingOffWfc) {
                 mButtonRtt.setSummary(TextUtils.concat(getText(R.string.rtt_mode_summary), "\n",
                         getText(R.string.no_rtt_when_roaming)));
             }
@@ -230,6 +241,21 @@
         return false;
     }
 
+    private boolean isOnWfc() {
+        LinkedBlockingQueue<Integer> result = new LinkedBlockingQueue<>(1);
+        Executor executor = Executors.newSingleThreadExecutor();
+        mContext.getSystemService(android.telephony.ims.ImsManager.class)
+                .getImsMmTelManager(SubscriptionManager.getDefaultSubscriptionId())
+                .getRegistrationTransportType(executor, result::offer);
+        try {
+            Integer transportType = result.poll(WFC_QUERY_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS);
+            return transportType != null
+                    && transportType == AccessNetworkConstants.TRANSPORT_TYPE_WLAN;
+        } catch (InterruptedException e) {
+            return false;
+        }
+    }
+
     private boolean shouldShowRttSetting() {
         // Go through all the subs -- if we want to display the RTT setting for any of them, do
         // display it.
diff --git a/src/com/android/services/telephony/TelecomAccountRegistry.java b/src/com/android/services/telephony/TelecomAccountRegistry.java
index 2975d06..b4b7405 100644
--- a/src/com/android/services/telephony/TelecomAccountRegistry.java
+++ b/src/com/android/services/telephony/TelecomAccountRegistry.java
@@ -55,6 +55,7 @@
 import android.text.TextUtils;
 
 import com.android.ims.ImsManager;
+import com.android.internal.telephony.LocaleTracker;
 import com.android.internal.telephony.Phone;
 import com.android.internal.telephony.PhoneFactory;
 import com.android.internal.telephony.SubscriptionController;
@@ -67,6 +68,7 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Optional;
+import java.util.function.Predicate;
 
 /**
  * Owns all data we have registered with Telecom including handling dynamic addition and
@@ -773,14 +775,51 @@
          * device.
          */
         private boolean isRttCurrentlySupported() {
+            // First check the emergency case -- if it's supported and turned on,
+            // we want to present RTT as available on the emergency-only phone account
+            if (mIsEmergency) {
+                // First check whether the device supports it
+                boolean devicesSupportsRtt =
+                        mContext.getResources().getBoolean(R.bool.config_support_rtt);
+                boolean deviceSupportsEmergencyRtt = mContext.getResources().getBoolean(
+                        R.bool.config_support_simless_emergency_rtt);
+                if (!(deviceSupportsEmergencyRtt && devicesSupportsRtt)) {
+                    Log.i(this, "isRttCurrentlySupported -- emergency acct and no device support");
+                    return false;
+                }
+                // Next check whether we're in or near a country that supports it
+                String country =
+                        mPhone.getServiceStateTracker().getLocaleTracker()
+                                .getCurrentCountry().toLowerCase();
+                String[] supportedCountries = mContext.getResources().getStringArray(
+                        R.array.config_simless_emergency_rtt_supported_countries);
+                if (supportedCountries == null || Arrays.stream(supportedCountries).noneMatch(
+                        Predicate.isEqual(country))) {
+                    Log.i(this, "isRttCurrentlySupported -- emergency acct and"
+                            + " not supported in this country: " + country);
+                    return false;
+                }
+                
+                return true;
+            }
+
             boolean hasVoiceAvailability = isImsVoiceAvailable();
 
             boolean isRttSupported = PhoneGlobals.getInstance().phoneMgr
                     .isRttEnabled(mPhone.getSubId());
 
             boolean isRoaming = mTelephonyManager.isNetworkRoaming(mPhone.getSubId());
+            boolean isOnWfc = mPhone.getImsRegistrationTech()
+                    == ImsRegistrationImplBase.REGISTRATION_TECH_IWLAN;
 
-            return hasVoiceAvailability && isRttSupported && !isRoaming;
+            boolean shouldDisableBecauseRoamingOffWfc = isRoaming && !isOnWfc;
+            Log.i(this, "isRttCurrentlySupported -- regular acct,"
+                    + " hasVoiceAvailability: " + hasVoiceAvailability + "\n"
+                    + " isRttSupported: " + isRttSupported + "\n"
+                    + " isRoaming: " + isRoaming + "\n"
+                    + " isOnWfc: " + isOnWfc + "\n");
+
+            return hasVoiceAvailability && isRttSupported && !shouldDisableBecauseRoamingOffWfc;
         }
 
         /**
@@ -1195,8 +1234,9 @@
 
         //We also need to listen for locale changes
         //(e.g. system language changed -> SIM card name changed)
-        mContext.registerReceiver(mLocaleChangeReceiver,
-                new IntentFilter(Intent.ACTION_LOCALE_CHANGED));
+        IntentFilter localeChangeFilter = new IntentFilter(Intent.ACTION_LOCALE_CHANGED);
+        localeChangeFilter.addAction(TelephonyManager.ACTION_NETWORK_COUNTRY_CHANGED);
+        mContext.registerReceiver(mLocaleChangeReceiver, localeChangeFilter);
 
         // Listen to the RTT system setting so that we update it when the user flips it.
         ContentObserver rttUiSettingObserver = new ContentObserver(