How Cable Messages are Transmitted.

South Canterbury Times, Issue 2762, 17 April 1900, Page 3

How Cable Messages are Transmitted.

A matter upon which the general newspaper reader is very commonly in error is as to the practicability of direct correspondence over such distances as lie between England and the Cape and the speed at which it is possible for messages to be conveyed. The actual conductor in submarine cables is a small copper core, surrounded by Insulating and protective material. After about 1000 miles the copper core has to be enlarged, or the transmission becomes slower. With the average cable about 100 letters a minute is considered very fair work. But they are able now to sendmessages simultaneously each way. This does not quite double the capacity of the cable, but it increases it by about 60 per cent. Working in each direction then, an ordinary submarine cable can transmit a total of about 160 letters a minute. But the limitation of distance is the source of a good deal of necessary delay, and also Is the fact that as yet it is not found practicable, except on short cables, to send messages from cables to land lines. Messages need to be telegraphed, and at the end of a certain length of cable also retelegraphing is necessary. Thus a message going from London to Capetown would first be transmitted by the ordinary land lines to Cornwall. There it will be written out for transmissiion to Gibraltar, where it will again be transcribed and despatched along the Mediterranean to Alexandria, There it will have to pass over a land line, and must, therefore, be once more written and sent in the usual way to Suez, where communication is again broken, and a fresh start given down the Red Sea to Aden, where there is another relay ready to pass it on to Zanzibar. From Zanzibar it will be treated as a new message, and will go to Mozambique. Here it will not be re-written, but just repeated on one instrument as ibis received from another. From Mozambique it finishes its sea passage at Durban, where it takes to the land again, and becomes a fresh message. In time of peace it may go round by way of Johannesburg to Capetown, but now it goes down the coast through Port Elizabeth. Thus a London message, by the time it reaches Capetown, will have been written eight times, and telegraphed nine times, in addition to all of which messages in war time are subject to military censorship, which necessarily causes delay. Nevertheless, a message was recently got through in half an hour, and the average time of transmission is shown by the company’s books to be 2 hours 30.41 minutes.— Daily News.