Canadian Pacific Railway Indicator Card, Larry Buchans collection, NAWCC

Canadian Pacific Railway Indicator Card - In order to ensure these standard clocks were always correct, a time signals was transmitted by telegraph once every 24 hours. If a clock was found to differ from the correct time by less than 10 seconds it was common practice for an indicator card to be placed on the clock indicating the variation from correct standard time. When the variation was 10 seconds or more the clock was to be reset.

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