be hung from the edge of a desk to communicate with different locations. Speaking tubes were also used in fine automobiles such as the 1927 Rolls-Royce Phantom, allowing communication between the separate passenger and driver's compartments when desired. Gosport tube A 'Gosport Tube' was a voice tube used by flight instructors in the early days of military aviation to give instructions and directions to their students. It was invented by flying instructor Robert Raymond Smith-Barry at the School of Special Flying he opened at Gosport in 1917. Modern usage Acoustic tube headphones (also called pneumatic earphones or air earphones) are used especially in two-way radio. These are useful because a clear tube can be used to hide the earphones. They are also sometimes used for the microphone on telephonists headsets and to provide music to patients undergoing an MRI scan, as it would be dangerous to use metal wiring in the scanner's magnetic field. In Europe, they were installed on the wards of hospitals for a time where the patient's "radio" was built into the nurse call and lighting control unit. This unit contains an electromagnetic conventional speaker but from there to the patient's ears was by tube, presumably so that the part contacting the patient could be easily cleaned. These systems are still in use. Pneumatic intercoms can be applied to motorcycle helmets for pilot-passenger communication. Similar systems are common on ultralight aviation too. They are sometimes preferred over Bluetooth or other radio technologies due to their simplicity and absence of batteries. Up to the 2000s acoustic tubes were in use in some civil aircraft for movies, audio and other audio broadcasting in-flight entertainment. The principle of the speaking tube can be found on certain playground equipment, which employs tubing connecting sound horns or other speaking boxes to allow voices to travel to separate points, for the amusement of the children. See also Acoustic transmission line Doppler fetal monitor Headphones History of the telephone Intercom Megaphone Pipe (fluid conveyance) Pneumatic tube Stethoscope Tin can telephone References External links Michele Gervais, "Empress of Ireland - Voice Tubes", Canadian Museum of Immigration at Pier 21 Maritime voice pipes and terrestrial speaking tubes, The Amplifier Institute Voicepipe usage proposed for a locomotive (never built), The Amplifier Institute History of telecommunications Telephony