public RAPDU Transmit(CAPDU capdu)
        {
            _capdu = capdu;

              if (!Transmit())
            return null;

              return _rapdu;
        }
        public void Transmit(CAPDU capdu, TransmitDoneCallback callback)
        {
            if (_transmit_thread != null)
            _transmit_thread = null;

              _capdu = capdu;

              if (callback != null)
              {
            _transmit_done_callback = callback;
            _transmit_thread = new Thread(TransmitFunction);
            _transmit_thread.Start();
              }
        }
        public bool Transmit(CAPDU capdu, ref RAPDU rapdu)
        {
            _capdu = capdu;

              if (!Transmit())
            return false;

              rapdu = _rapdu;
              return true;
        }