Posted by Peter H on October 22, 2007 at 21:01:40 from 86.130.122.72 user Peter_H.
In Reply to: Re: Signal Stations posted by Jock on October 22, 2007 at 19:50:13:
Long-distance semaphore systems were used successfully for maritime purposes. For example, from 1826 to 1861 the Holyhead to Liverpool telegraph was in use. This operated by means of signal arms on large masts (rather like huge railway signals). Between the end stations at Holyhead and Liverpool there were 9 or 10 relay stations along the coast. The passing of a named ship at Holyhead (or a signal received from that ship via flag code) could be relayed to the Liverpool waterfront in under 5 minutes. (It has been claimed that a signal once took only 27 seconds, but doubt has been cast on this.) The operation of the telegraph was complex, and of course it was of no use at night or in fog. Nevertheless it was highly successful until an electric telegraph replaced it. One or two of the relay stations can still be seen.
One of the secrets of a speedy semaphore telegraph system is the codification of the more common messages, and even some uncommon ones. Here are some of the hazard codes used on the Holyhead-Liverpool system: