diff --git a/lisainstrument/instrument.py b/lisainstrument/instrument.py
index ed01a96de98141242eb58d6236b6300125161008..f177d9c6db4d41000a773ca580543cb9631ab527 100644
--- a/lisainstrument/instrument.py
+++ b/lisainstrument/instrument.py
@@ -39,23 +39,25 @@ class Instrument:
     SCS = ForEachSC.indices()
     MOSAS = ForEachMOSA.indices()
 
-    # Supported laser locking topology
+    # Supported laser locking topologies (L12 as primary)
+    # pylint: disable=line-too-long
     LOCK_TOPOLOGIES = {
-        'N1': {'12': 'cavity', '23': 'adjacent', '31': 'distant', '13': 'adjacent', '32': 'adjacent', '21': 'distant'},
-        'N2': {'12': 'cavity', '23': 'adjacent', '31': 'distant', '13': 'adjacent', '32': 'distant', '21': 'distant'},
-        'N3': {'12': 'cavity', '23': 'adjacent', '31': 'adjacent', '13': 'adjacent', '32': 'distant', '21': 'distant'},
-        'N4': {'12': 'cavity', '23': 'distant', '31': 'distant', '13': 'adjacent', '32': 'adjacent', '21': 'distant'},
-        'N5': {'12': 'cavity', '23': 'distant', '31': 'distant', '13': 'adjacent', '32': 'adjacent', '21': 'adjacent'},
-        'N6': {'12': 'cavity', '23': 'adjacent', '31': 'adjacent', '13': 'distant', '32': 'distant', '21': 'distant'},
+        'N1': {'12': 'cavity', '23': 'adjacent', '31': 'distant',  '13': 'adjacent', '32': 'adjacent', '21': 'distant'},
+        'N2': {'12': 'cavity', '23': 'adjacent', '31': 'distant',  '13': 'adjacent', '32': 'distant',  '21': 'distant'},
+        'N3': {'12': 'cavity', '23': 'adjacent', '31': 'adjacent', '13': 'adjacent', '32': 'distant',  '21': 'distant'},
+        'N4': {'12': 'cavity', '23': 'distant',  '31': 'distant',  '13': 'adjacent', '32': 'adjacent', '21': 'distant'},
+        'N5': {'12': 'cavity', '23': 'distant',  '31': 'distant',  '13': 'adjacent', '32': 'adjacent', '21': 'adjacent'},
+        'N6': {'12': 'cavity', '23': 'adjacent', '31': 'adjacent', '13': 'distant',  '32': 'distant',  '21': 'distant'},
     }
 
-    INDEX_MAPS = {
+    # Index cycles for locking topologies
+    INDEX_CYCLES = {
         '12': {'12': '12', '23': '23', '31': '31', '13': '13', '32': '32', '21': '21'},
-        '23': {'12': '31', '23': '12', '31': '23', '13': '32', '32': '21', '21': '13'},
+        '21': {'12': '21', '23': '13', '31': '32', '13': '23', '32': '31', '21': '12'},
         '31': {'12': '23', '23': '31', '31': '12', '13': '21', '32': '13', '21': '32'},
-        '13': {'12': '13', '23': '21', '31': '32', '13': '12', '32': '31', '21': '23'},
-        '32': {'12': '21', '23': '32', '31': '13', '13': '23', '32': '12', '21': '32'},
-        '21': {'12': '32', '23': '13', '31': '21', '13': '31', '32': '23', '21': '12'},
+        '32': {'12': '32', '23': '21', '31': '13', '13': '31', '32': '12', '21': '23'},
+        '23': {'12': '31', '23': '12', '31': '23', '13': '32', '32': '21', '21': '13'},
+        '13': {'12': '13', '23': '32', '31': '21', '13': '12', '32': '23', '21': '31'},
     }
 
     def __init__(self,
@@ -460,8 +462,8 @@ class Instrument:
             if match:
                 self.lock_config = (match.group(1), match.group(2))
                 lock_12 = self.LOCK_TOPOLOGIES[self.lock_config[0]] # with 12 as primary
-                index_map = self.INDEX_MAPS[self.lock_config[1]] # correspondance to lock_12
-                self.lock = {mosa: lock_12[index_map[mosa]] for mosa in self.MOSAS}
+                cycle = self.INDEX_CYCLES[self.lock_config[1]] # correspondance to lock_12
+                self.lock = {mosa: lock_12[cycle[mosa]] for mosa in self.MOSAS}
             else:
                 raise ValueError(f"unsupported pre-defined locking configuration '{lock}'")
         elif isinstance(lock, dict):