How Does the Number of Tags Affect Reader Response?

I wonder about the response of tags to an RFID reader. If there is one tag, the interrogator will get one response; but if there are 200 tags, will the reader receive 200 responses? And does this differ for passive and active tags?

—Name withheld

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With a passive RFID system, a reader sends out radio waves that power up a tag and elicit a response. The air-interface protocol—the rules by which tags and interrogators communicate—includes an anti-collision algorithm that enables a reader to receive responses from multiple tags in sequence. This happens quickly, so it appears all of the tags are being read simultaneously.

Active tags, on the other hand, broadcast a signal. They can be awoken by a signal from a reader, or they can broadcast at a set interval. Active tags can also use anti-collision algorithms to ensure that more than one tag in a read field can be interrogated.

—Mark Roberti, Editor, RFID Journal