add direct routing to emergency calling

Author: boris-bazilevskiy

articles/communication-services/concepts/telephony/emergency-calling-concept.md

@@ -62,6 +62,11 @@ Emergency dialing is automatically enabled for all users of the Azure Communicat
 
 The Emergency service is temporarily free to use for Azure Communication Services customers within reasonable use, however, billing for the service will be enabled in 2022. Calls to 911 are capped at 10 concurrent calls per Azure resource.
 
+## Emergency calling with Azure Communication Services direct routing
+
+Emergency call is a regular call from a direct routing perspective. If you want to implement emergency calling with Azure Communication Services direct routing, you need to make sure that there is a routing rule for your emergency number (911, 112, etc.). You also need to make sure that your carrier processes emergency calls properly.
+there is also an option to use purchased number as a caller id for direct routing calls, in such case if there is no voice routing rule for emergency number, the call will fall back to Microsoft network, and we will treat it as a regular emergency call. Learn more about [voice routing fall back](./direct-routing-provisioning.md#voice-routing-considerations).
+
 ## Next steps
 
 ### Quickstarts