diff --git a/frappy_psi/parmod.py b/frappy_psi/parmod.py
index 0070026..31d60e0 100644
--- a/frappy_psi/parmod.py
+++ b/frappy_psi/parmod.py
@@ -149,7 +149,7 @@ class SwitchDriv(HasConvergence, Drivable):
     # disable_other = Parameter('whether to disable unused channel', BoolType(), readonly=False)
     selected = Parameter('selected module', EnumType(low=LOW, high=HIGH), readonly=False, default=0)
     autoswitch = Parameter('switch sensor automatically', BoolType(), readonly=False, default=True)
-    _switch_target = None  # if not None, switch to selection mhen mid range is reached
+    _switch_target = None  # if not None, switch to selection when mid range is reached
 
     # TODO: copy units from attached module
     # TODO: callbacks for updates
@@ -167,7 +167,7 @@ class SwitchDriv(HasConvergence, Drivable):
                     return
             else:
                 high = get_value(self.high, mid)  # return mid when high is invalid
-                if high < mid:
+                if high < mid:  # change to self.max_low
                     self.value = self.high.value
                     self._switch_target = None
                     self.write_target(self.target)
@@ -221,6 +221,7 @@ class SwitchDriv(HasConvergence, Drivable):
                 this, other = other, this
                 selected = HIGH
         elif target < self.min_high * 0.75 + self.max_low * 0.25:
+            # reinstall this with higher threshold (e.g. 4 K)?
             #if self.value > self.max_low:
             #    target1 = max(self.min_high, target)
             #    self._switch_target = LOW