diff --git a/hardware_system.py b/hardware_system.py
index 976a225b03c1583377f21e7ecb1dd09c93720160..fde8369457b3799d4b4fce255abdbc9c48e5dd92 100644
--- a/hardware_system.py
+++ b/hardware_system.py
@@ -325,7 +325,7 @@ class OhmPiHardware:
             time.sleep(activation_time)
             self.switch_mux(electrodes,roles, state='off')
         else:
-            for c in self._cabling.keys:
+            for c in self._cabling.keys():
                 self.switch_mux(electrodes=c[0],roles=c[1],state='on')
                 time.sleep(activation_time)
                 self.switch_mux(electrodes=c[0], roles=c[1], state='off')