Sense for a Type B Target is supported for 106, 212 and 424
        kbps. However, there may not be any target that understands the
        activation command in other than 106 kbps.

def sense_ttb(self, target):
        """Sense for a Type B Target is supported for 106, 212 and 424
        kbps. However, there may not be any target that understands the
        activation command in other than 106 kbps.

        """
        log.debug("polling for NFC-B technology")

        if target.brty not in ("106B", "212B", "424B"):
            message = "unsupported bitrate {0}".format(target.brty)
            raise nfc.clf.UnsupportedTargetError(message)

        self.chipset.in_set_rf(target.brty)
        self.chipset.in_set_protocol(self.chipset.in_set_protocol_defaults)
        self.chipset.in_set_protocol(initial_guard_time=20, add_sof=1,
                                     check_sof=1, add_eof=1, check_eof=1)

        sensb_req = (target.sensb_req if target.sensb_req else
                     bytearray.fromhex("050010"))

        log.debug("send SENSB_REQ " + hexlify(sensb_req))
        try:
            sensb_res = self.chipset.in_comm_rf(sensb_req, 30)
        except CommunicationError as error:
            if error != "RECEIVE_TIMEOUT_ERROR":
                log.debug(error)
            return None

        if len(sensb_res) >= 12 and sensb_res[0] == 0x50:
            log.debug("rcvd SENSB_RES " + hexlify(sensb_res))
            return nfc.clf.RemoteTarget(target.brty, sensb_res=sensb_res)