anchor.diff:  	% C.3.7 Called Party Number
   	{PhoneBin, OddEven} = encode_isup_party(PhoneNum),
   	<<OddEven:1, Nature:7, Inn:1, NumPlan:3, 0:4, PhoneBin/binary>>;
  -encode_isup_opt(?ISUP_PAR_CALLING_P_NUM,
  +encode_isup_par(?ISUP_PAR_CALLING_P_NUM,
   		#party_number{nature_of_addr_ind = Nature,
   			      number_incompl_ind = Ni,
   			      numbering_plan = NumPlan,
  
positive.code: 	% C.3.8 Calling Party Number
  	{PhoneBin, OddEven} = encode_isup_party(PhoneNum),
  	<<OddEven:1, Nature:7, Ni:1, NumPlan:3, PresRestr:2, Screen:2, PhoneBin/binary>>;
  encode_isup_opt(?ISUP_PAR_CONNECTED_NUM,
  		#party_number{nature_of_addr_ind = Nature,
  			      numbering_plan = NumPlan,
  			      present_restrict = PresRestr,
  
negative.code: 	% C.3.14 Connected Number
  	{PhoneBin, OddEven} = encode_isup_party(PhoneNum),
  	<<OddEven:1, Nature:7, 0:1, NumPlan:3, PresRestr:2, Screen:2, PhoneBin/binary>>;
  encode_isup_par(?ISUP_PAR_SUBSEQ_NUM,
  		#party_number{phone_number = PhoneNum}) ->
  	% C.3.32 Subsequent Number
  	{PhoneBin, OddEven} = encode_isup_party(PhoneNum),
  	<<OddEven:1, 0:7, PhoneBin/binary>>;
  encode_isup_par(Atom, More) when is_atom(Atom) ->
  	<<>>;
  encode_isup_par(OptNum, {OptLen, Binary}) when is_binary(Binary), is_integer(OptNum), is_integer(OptLen) ->
  	Binary.
  
  % encode a single OPTIONAL parameter (TLV type), skip all others
  encode_isup_optpar(ParNum, ParBody) when is_atom(ParNum) ->
  	<<>>;
  encode_isup_optpar(ParNum, ParBody) ->
  	ParBin = encode_isup_par(ParNum, ParBody),
  	ParLen = byte_size(ParBin),
  	<<ParNum:8, ParLen:8, ParBin/binary>>.
  
  % recursive function to encode all optional parameters 
  encode_isup_opts([], OutBin) ->
  	OutBin;
  encode_isup_opts([Opt|OptPropList], OutBin) ->
  	{OptType, OptBody} = Opt,
  	OptBin = encode_isup_optpar(OptType, OptBody),
  	encode_isup_opts(OptPropList, <<OutBin/binary, OptBin/binary>>).
  encode_isup_opts(OptPropList) ->
  	encode_isup_opts(OptPropList, <<>>).
  
  encode_isup_hdr(#isup_msg{msg_type = MsgType, cic = Cic}) ->
  	<<Cic:12/little, 0:4, MsgType:8>>.
  
  % Table C-16	Initial address
  encode_isup_msgt(?ISUP_MSGT_IAM, #isup_msg{parameters = Params}) ->
  	% Fixed part
  	CINat = proplists:get_value(conn_ind_nature, Params),
  	FwCallInd = proplists:get_value(fw_call_ind, Params),
  	CallingCat = proplists:get_value(calling_cat, Params),
  	TransmReq = proplists:get_value(transm_medium_req, Params),
  	PtrVar = 2, % one byte behind the PtrOpt
  	FixedBin = <<CINat:8, FwCallInd:16/big, CallingCat:8, TransmReq:8>>,
  	% V: Called Party Number
  	CalledParty = encode_isup_par(?ISUP_PAR_CALLED_P_NUM,
  					proplists:get_value(?ISUP_PAR_CALLED_P_NUM, Params)),
  	CalledPartyLen = byte_size(CalledParty),
  	% Optional part
  	PtrOpt = CalledPartyLen + 1 + 1, % 1 byte length, 1 byte start offset
  	OptBin = encode_isup_opts(Params),
  	<<FixedBin/binary, PtrVar:8, PtrOpt:8, CalledPartyLen:8, CalledParty/binary, OptBin/binary>>.
  
  encode_isup_msg(Msg = #isup_msg{msg_type = MsgType}) ->
  	HdrBin = encode_isup_hdr(Msg),
  	Remain = encode_isup_msgt(MsgType, Msg),
  	<<HdrBin/binary, Remain/binary>>.
  