function tapiRequestMakeCall(DestAddress, AppName,
CalledParty, Comment: PChar): Longint; stdcall; external 'TAPI32.DLL';

procedure TForm1.Button1Click(Sender: TObject);
var
PhoneNumber, AppName: array[0..255] of Char;
begin
PhoneNumber := '1234567890';
StrPCopy(AppName, Application.Title);
tapiRequestMakeCall(PhoneNumber, AppName, '', '');
end;
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