Page:Popular Science Monthly Volume 22.djvu/353

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TIME-KEEPING IN LONDON.

each provided with a projecting pin. When the signal arrives, the electro-magnet attracts its armature, and the two pins are brought close together. The mechanical operation will be understood by reference to Fig. 12, where a side elevation, a plan, and a front elevation are shown. This apparatus is fastened to ordinary clocks just back of the dial-plate (Fig. 13). A curved slot is cut through the dial for a short space on each side of XII, and through this the pins project. When, at the end of the hour, the signal arrives, the two pins are pushed together and bring the minute-hand exactly to XII. The position of the pins before and just after the operation is shown in Fig. 14. Evidently the clock must not be in error more than two minutes or so; but, as the hand is set every hour, any ordinary clock can be kept right by this device.

PSM V22 D353 Clock face with synchronizer attached.jpg
Fig. 13.—Face of Clock with Synchronizer attached. Fig. 14.

Other ingenious arrangements have been added to guard against danger, always present to long lines of wire, and for testing the condition of the lines, but a description of them can not here be given.

The advantages claimed for the system are:

 
1. That any number of clocks of any varying sizes can be synchronized to any agreed standard time-keeper.
 
2. That the mechanism is, when not in momentary use, entirely detached from the works of the clock.
 
3. That it can be applied to existing clocks.
 
4. That any failure in the transmission of the time-current leaves the clock going in the ordinary way, to be "set to time" by the next completed current.
 
5. That the clocks are kept to time whether having otherwise either a gaining or losing rate, even if such rate amounts to many minutes a day.