diff --git a/frappy_psi/picontrol.py b/frappy_psi/picontrol.py
index db3c1b0..eb95907 100644
--- a/frappy_psi/picontrol.py
+++ b/frappy_psi/picontrol.py
@@ -16,12 +16,14 @@
 # Module authors:
 #   Markus Zolliker <markus.zolliker@psi.ch>
 #   Jael Celia Lorenzana <jael-celia.lorenzana@psi.ch>
+#
 # *****************************************************************************
 
 """soft PI control"""
 
 import time
-from frappy.core import Writable, Attached, Parameter, FloatRange, Readable, BoolType, ERROR, IDLE
+import math
+from frappy.core import Writable, Parameter, FloatRange, IDLE
 from frappy.lib import clamp
 from frappy.datatypes import LimitsType, EnumType
 from frappy.mixins import HasOutputModule
@@ -30,8 +32,10 @@ from frappy.mixins import HasOutputModule
 class PImixin(HasOutputModule, Writable):
     p = Parameter('proportional term', FloatRange(0), readonly=False)
     i = Parameter('integral term', FloatRange(0), readonly=False)
-    output_range = Parameter('min output', LimitsType(FloatRange()), default=(0, 0), readonly=False)
-    output_func = Parameter('output function', EnumType(lin=0, square=1), readonly=False, default=0)
+    output_range = Parameter('min output',
+                             LimitsType(FloatRange()), default=(0, 0), readonly=False)
+    output_func = Parameter('output function',
+                            EnumType(lin=0, square=1), readonly=False, default=0)
     value = Parameter(unit='K')
     _lastdiff = None
     _lasttime = 0
@@ -50,10 +54,8 @@ class PImixin(HasOutputModule, Writable):
                 self._clamp_limits = lambda v, o=out: clamp(v, 0, o.read_limit())
             else:
                 self._clamp_limits = lambda v: v
-            self.log.info('OR %r', self.output_range)
             if self.output_range == (0.0, 0.0):
                 self.output_range = (0, self._clamp_limits(float('inf')))
-            self.log.info('OR %r', self.output_range)
         if not self.control_active:
             return
         self.status = IDLE, 'controlling'
@@ -68,7 +70,7 @@ class PImixin(HasOutputModule, Writable):
         out = self.output_module
         output = out.target
         if self.output_func == 'square':
-            output = match.sqrt(max(0, output))
+            output = math.sqrt(max(0, output))
         output += self.p * deltadiff + self.i * deltat * diff
         if self.output_func == 'square':
             output = output ** 2
@@ -79,21 +81,6 @@ class PImixin(HasOutputModule, Writable):
         if not value:
             self.output_module.write_target(0)
 
-    def write_target(self, target):
+    def write_target(self, _):
         if not self.control_active:
             self.activate_control()
-
-
-class PI(PImixin, Writable):
-    input = Attached(Readable, 'the input module')
-    relais = Attached(Writable, 'the interlock relais', mandatory=False)
-
-    def read_value(self):
-        return self.input.value
-
-    def write_target(self, value):
-        super().write_target(value)
-        if self.relais:
-            self.relais.write_target(1)
-
-