Semaphore (communication)

The semaphore line was a signalling system invented by the Chappe brothers in France. It is different from the naval semaphore system that uses hand-held flags, which was invented later.

Relative Costs

The semaphore system was cleverly designed, and provided a strategic advantage for France in a difficult time. However, it was almost 30 times more expensive per message than the electric telegraph. Here's a brief breakdown using $US:

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Semaphore line, 120 miles (Paris to Lille)

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• 15 towers ($1,500,000)
• At least 15 full-time operators ($450,000/year).
• Operates at most ten hours a day.
• Sends roughly 2 words per minute (1 symbol per minute, at 2 symbols per phrase, using the efficient directors' codebook).
• Cost to send one word one mile, at 10% interest: $0.0114

Electric Telegraph line, 120 miles

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• At least six full-time operators ($180,000/year)
• Poles, right-of-way, wires, installation: $15,000/mile, ($1,800,000)
• Operates 24 hours a day.
• Sends 15 words per minute (includes breaks for the operators).
• Cost to send one word one mile, at 10% interest: $0.000380