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RFID
Radio-frequency identification
(RFID) is an automatic identification method, relying on storing
and remotely retrieving data using devices called RFID tags
or transponders. An RFID tag is an object that can be attached
to or incorporated into a product, animal, or person for the
purpose of identification using radio waves. Passive tags require
no internal power source, whereas active tags require a power
source.
Passive
Passive RFID tags have no internal power supply. The minute
electrical current induced in the antenna by the incoming radio
frequency signal provides just enough power for the integrated
circuit in the tag to power up and transmit a response. Most
passive tags signal by backscattering the carrier signal from
the reader. This means that the antenna has to be designed to
both collect power from the incoming signal and also to transmit
the outbound backscatter signal.
Active
Unlike passive RFID tags, active RFID tags have their own internal
power source which is used to power any integrated circuits
that generate the outgoing signal. Active tags are typically
much more reliable (e.g. fewer errors) than passive tags due
to the ability for active tags to conduct a "session"
with a reader. Active tags, due to their onboard power supply,
also transmit at higher power levels than passive tags, allowing
them to be more effective in "RF challenged" environments
like water (including humans/cattle, which are mostly water),
or at longer distances.
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Alligator Gar
Lepisosteus spatula
Distribution : Mississippi River basin and
Gulf of Mexico
Diet in the wild : Fishes, waterfowl.
Do you know:
The alligator gar is the largest of all gars and can grow
up to 10 feet in length.
The hard scales on alligator gar protect it like a suit of
armor. South American natives use the scales as arrowheads
and also to decorate their tribal dresses.
The oldest gar fossil is from the Cretaceous Period of about
140 million years ago.
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Pacu
Piaractus brachypomum
Distribution : South America
Diet in the wild: Fruit, nuts, insects, small shellfish and
fish
Do you know :
Even though the pacu is a close relative of piranha, it is
a mild and peaceful fish.
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Freshwater Stingray
Potamotrygon sp.
Distribution : South America
Diet in the wild : Shrimps and small fishes
Do you know :
The motoro stingray is one of the many species of freshwater
stingrays in South America. Natives fear stepping on a freshwater
stingray accidentally as it would be very painful if injured
by the rays whipping tail and barbs.
Motoro stingrays are bred for their skin as leather for wallets,
handbags and belts.
Rays first appeared during the Jurassic period, about 200
million years ago.
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