frameworks/base/telecomm/java/android/telecom/TelecomManager.java
 public static TelecomManager from(Context context) {

        return (TelecomManager) context.getSystemService(Context.TELECOM_SERVICE);

     }

 frameworks/base/telephony/java/android/telephony/TelephonyManager.java
 private ITelecomService getTelecomService() {

          return ITelecomService.Stub.asInterface(ServiceManager.getService(TELECOM_SERVICE));

    }

frameworks/base/core/java/android/app/SystemServiceRegistry.java  
registerService(Context.TELECOM_SERVICE, TelecomManager.class,

                 new CachedServiceFetcher<TelecomManager>() {

             @Override

             public TelecomManager createService(ContextImpl ctx) {

                  return new TelecomManager(ctx.getOuterContext());

            }});

frameworks/base/services/core/java/com/android/server/telecom/TelecomLoaderService.java
public class TelecomLoaderService extends SystemService {

 private class TelecomServiceConnection implements ServiceConnection {

          @Override

          public void onServiceConnected(ComponentName name, IBinder service) {                      ...              ServiceManager.addService(Context.TELECOM_SERVICE, service);
          }
        ...

         @Override

         public void onServiceDisconnected(ComponentName name) {

            connectToTelecom();

         }