WALLS THAT SPEAK.

Manawatu Herald, Volume XXXV, Issue 1108, 12 June 1913, Page 4

WALLS THAT SPEAK.

Passengers passing through the colossal new Grand Central Terminal in New York are experiencing the novel sensation of being periodically addressed by voices that emanate from the walls about them. They sit comfortably in secluded reception and waiting rooms and hear the arriving and departing trains announced to them in clear, distinct tones whose source is absolutely invisible. The “mystery,” which has astonished not a few provincial visitors, is an electrical device invented to supplant the now outlived organvoiced official who formerly chanted information as to the movements of trains. The advice is called an “electric announcer,” and is really only a telephone with a receiver actuated by an electric current of unusually high voltage. It is described in Popular Electricity Magazine thus : “Thirtysix megaphone transmitters are hidden in the walls of the various rooms of the station, These are operated by only one announcer, who talks in an ordinary tone into a single transmitter at a central point. The principle involved is something different from anything in use for the same purpose anywhere else iu the world. The transmitter contains no induction coil, and is surrounded by a waterjacket, through which a tiny stream of cold water flows constantly, cooling the carbon, which would otherwise become packed with the heat of the heavy current of ito volts used in operating the announcer. The ordinary telephone requires only a small fraction of this amount, but it is through the employment of the heavy voltage that the remarkable results are obtained. The voltage is so equalised and the circuits are so balanced , on the Wheatstone principle that the sound of the human voice is intensified many times. And there is no limit to the number of points to which wires may be run for the transmission of sound from the central point.”