diff --git a/frappy/datatypes.py b/frappy/datatypes.py
index 30b7840..e8240a8 100644
--- a/frappy/datatypes.py
+++ b/frappy/datatypes.py
@@ -1244,16 +1244,20 @@ UInt64 = IntRange(0, (1 << 64) - 1)
 
 # Goodie: Convenience Datatypes for Programming
 class LimitsType(TupleOf):
-    def __init__(self, members):
-        super().__init__(members, members)
+    def __init__(self, member):
+        super().__init__(member, member)
 
-    def __call__(self, value):
+    def validate(self, value, previous=None):
         """accepts an ordered tuple of numeric member types"""
-        limits = TupleOf.validate(self, value)
+        limits = TupleOf.validate(self, value, previous)
         if limits[1] < limits[0]:
-            raise RangeError(f'Maximum Value {limits[1]} must be greater than minimum value {limits[0]}!')
+            raise RangeError(f'maximum value {limits[1]} must be greater than '
+                             f'minimum value {limits[0]}')
         return limits
 
+    def copy(self):
+        return LimitsType(TupleOf.copy(self).members[0])
+
 
 class StatusType(TupleOf):
     """convenience type for status
diff --git a/frappy_mlz/entangle.py b/frappy_mlz/entangle.py
index 7b7d599..62925af 100644
--- a/frappy_mlz/entangle.py
+++ b/frappy_mlz/entangle.py
@@ -620,20 +620,14 @@ class AnalogOutput(PyTangoDevice, Drivable):
 
     del __getusermin, __setusermin, __getusermax, __setusermax
 
-    def _checkLimits(self, limits):
-        umin, umax = limits
+    def write_userlimits(self, value):
+        umin, umax = value
         amin, amax = self.abslimits
-        if umin > umax:
-            raise RangeError(
-                f'user minimum ({umin}) above the user maximum ({umax})')
         if umin < amin - abs(amin * 1e-12):
             umin = amin
         if umax > amax + abs(amax * 1e-12):
             umax = amax
-        return (umin, umax)
-
-    def write_userlimits(self, value):
-        return self._checkLimits(value)
+        return umin, umax
 
     def write_target(self, value=FloatRange()):
         umin, umax = self.userlimits