diff --git a/frappy_psi/bkpower.py b/frappy_psi/bkpower.py
index 2171ab8..7b2cb92 100644
--- a/frappy_psi/bkpower.py
+++ b/frappy_psi/bkpower.py
@@ -17,51 +17,80 @@
 #   Markus Zolliker <markus.zolliker@psi.ch>
 #   Jael Celia Lorenzana <jael-celia.lorenzana@psi.ch>
 # *****************************************************************************
-"""Powersupply B&K Precision BK168xB"""
+"""Powersupply B&K Precision BK168xB
+
+The following lines are part of a config file for the  frappy-server process
+The frappy server creates the following modules and refreshes the values with a refresh rate  of 1 sec.
+The communication with the powersupply is established via serial over USB.
+The manual can be found here  https://www.vectortechnologies.gr/images/products/2022/02/168xB_programming_manual.pdf
+
+Mod('htr_io',
+    'frappy_psi.bkpower.IO',
+    'powersupply communicator',
+    uri = 'serial:///dev/ttyUSBupper',
+   )
+
+Mod('htr',
+    'frappy_psi.bkpower.Power',
+    'heater power',
+    io= 'htr_io',
+   )
+
+Mod('out',
+    'frappy_psi.bkpower.Output',
+    'heater output',
+    io = 'htr_io',
+    maxvolt = 50,
+    maxcurrent = 2,
+   )
+"""
+
 
 from frappy.core import StringIO, Readable, Parameter, FloatRange, Writable, HasIO, BoolType
 
+
+# define the IO class
 class IO(StringIO):
     end_of_line = ('OK\r', '\r')
     default_settings = {'baudrate': 9600}
-    
-    
+
+
 class Power(HasIO, Readable):
     value = Parameter(datatype=FloatRange(0,300,unit='W'))
-    
+
     def read_value(self):
         reply = self.communicate('GETD')
         volt = float(reply[0:4])/100
         current = float(reply[4:8])/100
         return volt*current
 
-    
+
 class Output(HasIO, Writable):
     value = Parameter(datatype=FloatRange(0,100,unit='%'))
     target = Parameter(datatype=FloatRange(0,100,unit='%'))
     maxvolt = Parameter('voltage at 100%',datatype=FloatRange(0,60,unit='V'),default=50,readonly=False)
     maxcurrent = Parameter('current at 100%',datatype=FloatRange(0,5,unit='A'),default=2,readonly=False)
     output_enable = Parameter('control on/off', BoolType(), readonly=False)
-    
+
     def initModule(self):
         super().initModule()
         self.write_output_enable(False)
-        
+
     def write_target(self, target):
         self.write_output_enable(target != 0)
         self.communicate(f'VOLT{round(max(8,target*self.maxvolt/10)):03d}')
         self.communicate(f'CURR{round(target*self.maxcurrent):03d}')
         self.value = target
-        
+
     def write_output_enable(self, value):
         self.communicate(f'SOUT{int(not value)}')
-        
+
     def write_maxvolt(self, maxvolt):
         self.communicate(f'SOVP{round(maxvolt*10):03d}')
-        
+
     def write_maxcurrent(self, maxcurrent):
         self.communicate(f'SOCP{round(maxcurrent*100):03d}')
-        
+
     def shutdown(self):
         self.write_target(0)
-    
+