diff --git a/pySim/transport/__init__.py b/pySim/transport/__init__.py
index 8055306d..5b0ee076 100644
--- a/pySim/transport/__init__.py
+++ b/pySim/transport/__init__.py
@@ -119,6 +119,11 @@ class LinkBase(abc.ABC):
         """Connect to a card immediately
         """
 
+    @abc.abstractmethod
+    def get_atr(self) -> Hexstr:
+        """Retrieve card ATR
+        """
+
     @abc.abstractmethod
     def disconnect(self):
         """Disconnect from card
diff --git a/pySim/transport/calypso.py b/pySim/transport/calypso.py
index fa3a9f29..f28e40c6 100644
--- a/pySim/transport/calypso.py
+++ b/pySim/transport/calypso.py
@@ -123,6 +123,9 @@ class CalypsoSimLink(LinkBaseTpdu):
     def connect(self):
         self.reset_card()
 
+    def get_atr(self) -> Hexstr:
+        return "3b00" # Dummy ATR
+
     def disconnect(self):
         pass  # Nothing to do really ...
 
diff --git a/pySim/transport/modem_atcmd.py b/pySim/transport/modem_atcmd.py
index e7614c0e..440ec779 100644
--- a/pySim/transport/modem_atcmd.py
+++ b/pySim/transport/modem_atcmd.py
@@ -139,6 +139,9 @@ class ModemATCommandLink(LinkBaseTpdu):
     def connect(self):
         pass  # Nothing to do really ...
 
+    def get_atr(self) -> Hexstr:
+        return "3b00" # Dummy ATR
+
     def disconnect(self):
         pass  # Nothing to do really ...