<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">sound mirrors</topic></authority><related type="broader"><topic>communications structures</topic></related><variant type="other"><topic>acoustical sound mirrors</topic></variant><variant type="other"><topic>listening posts</topic></variant><variant type="other"><topic>mirrors, sound</topic></variant><variant type="other"><topic>sound mirror</topic></variant> <note xml:lang="en"><![CDATA[ Concrete structures of various forms, usually including a concrete dish linked to microphones, acting as early warning systems to detect and transmit the sound of incoming zeppelins; installed along the English coast facing Europe during the early 20th century. ]]></note></mads>