How Everything Works

poliss · How Everything Works

From steam engines to light bulbs, watches to locks, bikes and threshers. It's all here in this mini encyclopedia from the 1930s

Extract from the Railway Signlling section.
"A signalman cannot lower or restore his signals to their normal positions in any order he likes. He is compelled to lower them as follows:—Starting and home; then distant. And restore them—distant; then starting and home. If a signalman were quite independent, he might, after the passage of a train, restore the home or starting, but forget all about the distant, so that the next train, which he wants to stop, would dash past the distant without warning and have to pull up suddenly when the home came in sight. But by a mechanical arrangement he is prevented[Pg 205] from restoring the home or starting until the distant is at danger; and, vice versâ, he cannot lower the last until the other two are off. This mechanism is called locking gear."

http://www.gutenberg.org/files/28553/28553-h/28553-h.htm

upnick

Fascinating stuff Poliss