Early Telegraph Systems

Question

My understanding of telegraphs is that you can only send one message at a time over one cable, if that is not accurate then this question is pointless.

I am curious how telegraph communication was run when the cables were first laid on the bottom of the ocean (E.g. Britain to India). Did they lay multiple cables or just one? How did they keep other organizations from cutting them where they came up from the water, and if someone did how long did it take them to find the damaged spot and repair it? Was the government and business competing over availability of telegraph lines? If so how did this play out?

Answer 1

To get all the way to India would take several steps. At the turn of the century there were three cables from Aden to Bombay. So, if you needed to wire Madras from London, the message would first have to be sent to Aden, then to Bombay, then on to Madras.

In general, most of the long line pre-WW2 cables were single conductor only (one channel). Here is a typical design:

So, a message can only be sent in one direction at a given time. The telegraph operators had conventions for negotiating the exchange. For example, if an operator had no more words to send he might signal NM, meaning "no more". To tell the other operator you are ready to receive you could send GA (go ahead). Duplex or quadraplex systems were more common on land.

Damage to cables was (and is) a constant problem. Usually the damage is accidental and is caused by a trawler or by a ship anchor. The cables are designed to be very tough, so it is hard to break them, even for a big ship. Shifting sands often bury cables, so in many cases you cannot even tell that they are there.

If a cable is damaged, then a cable ship goes out to repair it. It uses a special hook to grab it and drag it to the surface. Cable ships have special equipment for testing cables. How long it would take to repair a line depends on a lot of different factors, so it might be a few days or few weeks.

In many cases the government and the military, in particular, would have priority over transmissions. Telegraph cables have almost always been commercial ventures, though, so the government had to pay just like everybody else.

Answer 2

All this is described in many books on the history of laying the first transatlantic cable. For example, in J. S. Gordon, A thread across the ocean, Walker, NY, 2002. The story is too long ans exciting to tell it here but some of your questions can be answered shortly.

1. The early cables handled one message at a time. Moreover, the transmission was very slow. It took many hours to transmit a short message on the first cable. The engineers tried to experiment sending sharper and sharper signals, and burned the cable after few weeks of the experiment. New cable had to be layed.

2. The places near the shore where the cable passed had to be marked and protected. One of the first cables was picked by a fisherman who first thought that this was a sea monster (looking like a snake). He could not pull the whole monster, so he decided to cut it... and found something looking like gold inside!!!

3. After the first cable was burned, the company was bankrupt, and it was difficult to restart the business because investors lost their trust after many years of failures. So the project was strongly supported by the British crown. The reason was that on the first cable (which lived about a week or so) the government managed to transmit an important telegram to Canada. The money saved because of this telegram was more than the price of the laying the cable:-) (This was about some substantial troop movement from Canada to India). Based on this story I suppose the government had some priority, especially after it helped to finance the first successful project.

These and very many other similar stories are contained in this book, and I suppose in many other books written on the subject. The publicity for these first cables was comparable with publicity of the first Moon landings. This was indeed an amazing "project of the century".

I wonder why Jules Verne did not write a novel about this. The real events were more exciting than the plots of most of his novels. The cable is only mentioned in the last lines of his "Round the Moon". The landing astronauts are picked by a cable-laying ship.