Voicepipe
Voicepipes were rigid or flexible speaking tubes running between stations on a ship between which reliable oral communication was helpful. They were a common tool in all navies, and popular for their relatively fail-safe nature in combat.
Form Factor
Many voice pipes intended for sporadic communication had covers with whistles in them, and the means of calling up the remote station was to remove the cover on your end, place your mouth over a mouthpiece and blow vigourously into the tube to cause the whistle at the other end to sound.
Voicepipes were not always very useful in spaces where the sound of machinery or conversations of others could get in the way. It was common practice in such places for voicepipes and navyphones to be allotted an enclosed space called a "silent cabinet", which must have often been a relative term.
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