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A whistle post (or whistle board), in railroad usage, is a sign marking a location where a locomotive engineer is required to sound the horn or whistle. ==United States== Whistle posts in the United States were traditionally placed about one-quarter mile in advance of a road crossing. The signs in themselves varied in design from railroad to railroad. Some were marked with – – o – (two longs, one short, and another long) in a similar manner of sending the letter Q in Morse Code. This sequence is known as ''Rule 14(l)'' " Rule # 14(l) - Approaching public crossings at grade, to be prolonged or repeated until crossing is reached unless otherwise provided". This rule is applied in almost all U.S. railroad operating rule books even if the advance warning provided by the horn will be less than 15 seconds in duration. This signal is to be prolonged or repeated until the engine or train occupies the crossing; or, where multiple crossing are involved, until the last crossing is occupied. The same rule is practiced when approaching locations such as rail yards, where men may be working on the tracks, as well as bridges, tunnels and other points. Modern whistle posts are of simple sheet metal construction, utilizing a 'W' marker. Some multiple crossings protected by a single sign have an 'X' displayed below the 'W', other multiple crossings may have 2 or 3 W markers on the same post. Whistle posts used on the former Southern Pacific display an 'X'. Multiple crossings have a number displayed beneath the 'X' for the number of crossings. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Whistle post」の詳細全文を読む スポンサード リンク
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