diff --git a/pySim/construct.py b/pySim/construct.py
index 6daa66a..fcbadd8 100644
--- a/pySim/construct.py
+++ b/pySim/construct.py
@@ -2,7 +2,7 @@
 from construct.core import EnumIntegerString
 import typing
 from construct import *
-from construct.core import evaluate, bytes2integer, integer2bytes
+from construct.core import evaluate, bytes2integer, integer2bytes, BitwisableString
 from construct.lib import integertypes
 from pySim.utils import b2h, h2b, swap_nibbles
 import gsm0338
@@ -44,6 +44,25 @@
     def _encode(self, obj, context, path):
         return h2b(swap_nibbles(obj))
 
+class InvertAdapter(Adapter):
+    """inverse logic (false->true, true->false)."""
+    @staticmethod
+    def _invert_bool_in_obj(obj):
+        for k,v in obj.items():
+            # skip all private entries
+            if k.startswith('_'):
+                continue
+            if v == False:
+                obj[k] = True
+            elif v == True:
+                obj[k] = False
+        return obj
+
+    def _decode(self, obj, context, path):
+        return self._invert_bool_in_obj(obj)
+
+    def _encode(self, obj, context, path):
+        return self._invert_bool_in_obj(obj)
 
 class Rpad(Adapter):
     """
@@ -228,3 +247,11 @@
             data = swapbytes(data)
         stream_write(stream, data, length, path)
         return obj
+
+# merged definitions of 24.008 + 23.040
+TypeOfNumber = Enum(BitsInteger(3), unknown=0, international=1, national=2, network_specific=3,
+                    short_code=4, alphanumeric=5, abbreviated=6, reserved_for_extension=7)
+NumberingPlan = Enum(BitsInteger(4), unknown=0, isdn_e164=1, data_x121=3, telex_f69=4,
+                     sc_specific_5=5, sc_specific_6=6, national=8, private=9,
+                     ermes=10, reserved_cts=11, reserved_for_extension=15)
+TonNpi = BitStruct('ext'/Flag, 'type_of_number'/TypeOfNumber, 'numbering_plan_id'/NumberingPlan)
diff --git a/pySim/ts_51_011.py b/pySim/ts_51_011.py
index f9f1e2a..c29b54c 100644
--- a/pySim/ts_51_011.py
+++ b/pySim/ts_51_011.py
@@ -402,8 +402,42 @@
 
 # TS 51.011 Section 10.5.6
 class EF_SMSP(LinFixedEF):
+    class ValidityPeriodAdapter(Adapter):
+        def _decode(self, obj, context, path):
+            if obj <= 143:
+                return obj + 1 * 5
+            elif obj <= 167:
+                return 12 * 60 + ((obj - 143) * 30)
+            elif obj <= 196:
+                return (obj - 166) * (24 * 60)
+            elif obj <= 255:
+                return (obj - 192) * (7 * 24 * 60)
+            else:
+                raise ValueError
+        def _encode(self, obj, context, path):
+            if obj <= 12*60:
+                return obj/5 - 1
+            elif obj <= 24*60:
+                return 143 + ((obj - (12 * 60)) / 30)
+            elif obj <= 30 * 24 * 60:
+                return 166 + (obj / (24 * 60))
+            elif obj <= 63 * 7 * 24 * 60:
+                return 192 + (obj / (7 * 24 * 60))
+            else:
+                raise ValueError
+
     def __init__(self, fid='6f42', sfid=None, name='EF.SMSP', desc='Short message service parameters', **kwargs):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len={28, None}, **kwargs)
+        ScAddr = Struct('length'/Int8ub, 'ton_npi'/TonNpi, 'call_number'/BcdAdapter(Rpad(Bytes(10))))
+        self._construct = Struct('alpha_id'/COptional(GsmStringAdapter(Rpad(Bytes(this._.total_len-28)))),
+                                 'parameter_indicators'/InvertAdapter(FlagsEnum(Byte, tp_dest_addr=1, tp_sc_addr=2,
+                                                                                tp_pid=3, tp_dcs=4, tp_vp=5)),
+                                 'tp_dest_addr'/ScAddr,
+                                 'tp_sc_addr'/ScAddr,
+
+                                 'tp_pid'/HexAdapter(Bytes(1)),
+                                 'tp_dcs'/HexAdapter(Bytes(1)),
+                                 'tp_vp_minutes'/EF_SMSP.ValidityPeriodAdapter(Byte))
 
 # TS 51.011 Section 10.5.7
 class EF_SMSS(TransparentEF):