![]() ![]() Railways were among the first customers for time signals, which allowed synchronization of their operations over wide geographic areas. The advent of electrical telegraphs allowed widespread and precise distribution of time signals from central observatories. Busy sea ports used a visual signal, the dropping of a ball, to allow mariners to check the chronometers used for navigation. These automatic signal clocks were synchronized by telegraphy in 1905 before the widespread use of radioĪ time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.Ĭhurch bells or voices announcing hours of prayer gave way to automatically operated chimes on public clocks however, audible signals (even signal guns) have limited range. ![]()
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