Page:Popular Science Monthly Volume 22.djvu/354

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THE POPULAR SCIENCE MONTHLY.

In London the system has been in successful operation for about five years, and has been used over a wire four hundred miles long. The subscribers number about five hundred, among them many rail-roads and public institutions.

In connection with the synchronized clocks, Messrs. Barraud and Lund have also established time-bells and flashing-signals, which afford

PSM V22 D354 Barraud and lund time bell.jpg
Fig. 15 Barraud and Lund's Time-Bell.

time-signals both to the ear and eye. These are shown in Figs. 15 and 16. The bell is an ordinary electric bell, and is rung by the regulating clock, which closes the circuit at the instant the signal is desired. The flashing-signal consists of a red vertical disk on a vertical axis, which normally shows only its edge, but is made to revolve once on its axis in four sudden jumps, by simple mechanism in connection with electro-magnets, when the regulator, by closing the circuit, sends the current. The appearance is that of two flashes of red as the disk revolves.

In many places where noise prevents hearing a bell, the flashing-signal becomes a necessity. It is in use at the London Stock Ex-