diff --git a/acs.coffee b/acs.coffee
index b9930a6..3dfd7d8 100644
--- a/acs.coffee
+++ b/acs.coffee
@@ -5,7 +5,7 @@ http = require 'http'
 https = require 'https'
 tr069 = require './tr-069'
 tasks = require './tasks'
-sanitize = require('./sanitize').sanitize
+normalize = require('./normalize').normalize
 db = require './db'
 presets = require './presets'
 mongodb = require 'mongodb'
@@ -45,18 +45,21 @@ updateDevice = (currentRequest, actions, callback) ->
 
   now = new Date(Date.now())
   updates = {}
+  deletes = {}
   if actions.inform
     updates['_last_inform'] = now
 
   if actions.parameterValues?
     for p in actions.parameterValues
-      v = sanitize(p[0], p[1])
+      origValue = p[1]
+      v = normalize(p[0], origValue)
+
       path = if common.endsWith(p[0], '.') then p[0] else "#{p[0]}."
-      if v is undefined
-        updates["#{path}_value"] = p[1]
+      if v == origValue
+        deletes["#{path}_orig"] = 1
       else
-        updates["#{path}_value"] = v
-        updates["#{path}_orig"] = p[1]
+        updates["#{path}_orig"] = origValue
+      updates["#{path}_value"] = v
       updates["#{path}_timestamp"] = now
 
   if actions.parameterNames?
@@ -68,7 +71,7 @@ updateDevice = (currentRequest, actions, callback) ->
       updates["#{path}_timestamp"] = now
 
   if Object.keys(updates).length > 0
-    db.devicesCollection.update({'_id' : currentRequest.deviceId}, {'$set' : updates}, {safe: true}, (err, count) ->
+    db.devicesCollection.update({'_id' : currentRequest.deviceId}, {'$set' : updates, '$unset' : deletes}, {safe: true}, (err, count) ->
       if (err)
         callback(err) if callback?
         return
diff --git a/normalize.coffee b/normalize.coffee
new file mode 100644
index 0000000..1032160
--- /dev/null
+++ b/normalize.coffee
@@ -0,0 +1,39 @@
+common = require './common'
+
+
+normalizers = {}
+
+
+FLOAT_REGEX = /^([\-\+]?[0-9\.]+)/
+normalizers.float = (input) ->
+  res = FLOAT_REGEX.exec(input)
+  if res != null
+    parseFloat(res[1])
+  else
+    null
+
+
+exports.normalize = (path, value) ->
+  if path of parameters
+    return normalizers[parameters[path].type](value)
+  else
+    return value
+
+
+parameters = {
+  'InternetGatewayDevice.WiMAX.Status.RSSI' : {
+    type : 'float',
+  },
+  'InternetGatewayDevice.WiMAX.Status.CINR1' : {
+    type : 'float',
+  },
+  'InternetGatewayDevice.WiMAX.Status.CINR2' : {
+    type : 'float',
+  },
+  'InternetGatewayDevice.X_MTK_WiMAX_Param.CINR_level' : {
+    type : 'float',
+  },
+  'InternetGatewayDevice.X_MTK_WiMAX_Param.RSSI_level' : {
+    type : 'float',
+  },
+}
\ No newline at end of file
diff --git a/sanitize.coffee b/sanitize.coffee
deleted file mode 100644
index 57e2fb4..0000000
--- a/sanitize.coffee
+++ /dev/null
@@ -1,23 +0,0 @@
-FLOAT_REGEX = /^([\-\+]?[0-9\.]+)/
-
-extractFloat = (numStr) ->
-  res = FLOAT_REGEX.exec(numStr)
-  if res != null
-    parseFloat(res[1])
-  else
-    null
-
-exports.sanitize = (path, value) ->
-  switch path
-    when 'InternetGatewayDevice.WiMAX.Status.RSSI'
-      extractFloat(value)
-    when 'InternetGatewayDevice.WiMAX.Status.CINR1'
-      extractFloat(value)
-    when 'InternetGatewayDevice.WiMAX.Status.CINR2'
-      extractFloat(value)
-    when 'InternetGatewayDevice.X_MTK_WiMAX_Param.CINR_level' # Seowon devices
-      extractFloat(value)
-    when 'InternetGatewayDevice.X_MTK_WiMAX_Param.RSSI_level' # Seowon devices
-      extractFloat(value)
-    else
-      undefined