Echo Filter

The is a technology used to see beyond obstacles using ultrasonic waves.
==Principles==
It is similar to the that is used on pregnant women to look on the fetus inside a womb, however, the output was stronger.
Originally, the idea of using ultrasound to scan beyond obstacles was derived from research in applications dealing with counter-terrorist operations. However, since the images often end up vague as a result (making it difficult to tell who the person that the ultrasound revealed), it had gone for many years without becoming widely used. Sub.27
The device can apparently be used in a smart phone.
==Chronology==
===Shinyaku Toaru Majutsu no Index===
====Baggage City Arc====
The Echo Filter is first used by Kihara Enshuu in order to figure out what's behind a certain room's contents. Here, she discovers that Ayles Bigant is behind the door, and later uses a remotely controlled crane to smash down on his hiding place, crushing him, though not killing him.
==References==
Category:Terminology
Category:Science
Category:Academy City Technology