If an RFID reader continuously emits radio waves, then what about its wastage power if no tag is there?
No, active antennas do not broadcast all the time. Readers can be set to emit energy on a predefined duty cycle. This means you can have one emit energy for a minute, stop for 10 minutes, emit for another minute and so forth. You can also set up the device to emit energy only when an electric eye is tripped, indicating there is something approaching that needs to be interrogated. For an active real-time locating system, the tags send out a signal, and the readers simply receive it.
—Mark Roberti, Founder and Editor, RFID Journal
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