A speaking tube or voicepipe is a device based on two cones connected by an air pipe through which speech can be transmitted over an extended distance. Use of pipes was suggested by Francis Bacon in the New Atlantis (1672). The usage for telecommunications was experimented and proposed for administrative communications in 1782 by the French monk Dom Gauthey in a memorandum communicated to the Académie des Sciences. Dom Gauthey launched a subscription supported by Benjamin Franklin and other French scientists to finance further experiments, but was not able to raise enough money to go ahead. The British utilitarist philosopher Jeremy Bentham proposed the inclusion of "conversation tubes" in the architecture of his Panopticon (1787, 1791, 1811) and then as a means of military telecommunication (1793) and at the end as a necessary equipment in the architecture of ministries (1825). While its most common use was in intra-ship communications, the principle was also used in affluent homes and offices of the 19th century, as well as expensive automobiles, military aircraft, and even locomotives. For most purposes, the device was outmoded by the telephone and its widespread adoption. Design Early voicepipes consisted of two cones, of wood or metal, one end shaped to fit the speaker's mouth, connected to the other which was flared to amplify the sound (specifically to match the impedance of the tube to that of the open room). Later designs of the voicepipe inserted a removable cork-mounted whistle, which could be sounded by blowing into the tube from the other end. On naval vessels, this created a distinctive sound associated with urgent intra-ship communication. The sound of the whistle would summon the listener, who would remove the whistle and answer the call. Voice pipes could be used over distances as long as . However, very long speaking tubes might use an electrical signalling device to indicate a call, as the large volume of air in the pipe would make it difficult to blow with enough pressure to sound a whistle at the far end. Despite this, a pipe with a larger internal diameter was desirable for longer runs as the signal loss is inversely proportional to the pipe's cross-sectional area. Voicepipes have no switching mechanism and so, to provide multiple destinations, separate voicepipes with dedicated transit pipes have to be provided between all pairs of desired endpoints. The technology continues to be used into the electronic age