A semi-active tag is an RFID tag that uses a battery to communicate but remains dormant until an RFID reader sends an energizing signal. The tag can then use its battery to communicate with the reader. Semi-active tags have a longer range than passive tags and a longer battery life than active tags. Their main advantage relative to active tags is that they have a longer battery life. The waking process, however, sometimes causes an unacceptable time delay when RFID tags pass readers very quickly or when many RFID tags need to be read within a very short period of time. Some literature uses the terms “semi-passive” and “semi-active” interchangeably.