What is another word for speaking tube?
Pronunciation: [spˈiːkɪŋ tjˈuːb] (IPA) 
The term "speaking tube" refers to an older communication device that allows for one-way communication from one location to another. This device can also be referred to as a voice tube, intercom tube, or tube communication system. Other synonyms for the term include voice-pipe, talk-tube, and speak-tube. Although these devices are not commonly used in modern times, they were once an important method of communication in factories, ships, and other industrial settings. Speaking tubes are still sometimes used in historical reenactments, but newer technology has made them largely obsolete. Overall, speaking tube synonyms demonstrate the many ways in which people have attempted to communicate over long distances throughout history.
