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PUBLIC RECORD
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Reference :-
C.O. 885
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PACIFIC CABLE COMMITTEE:
25. On the question of the deductions which have to be made to reduce the theoretical to the practical speed, the divergence of opinion was not less remarkable.
26. The explanation of this is to be found in the fact that much depends upon the system on which a line is worked. Thus, in the case of the trans-Atlantic lines, where the competition is very keen and the hours of business comparatively limited, and where the regulations of the International Telegraphic Convention do not apply, it has been found possible to reduce the non-paying traffic to about 16 per cent.
27. On the other hand, on the Eastern lines the proportion is much higher because the reserve power of the lines is very great, and, therefore, there is more margin for non- paying traffic, the working hours are practically longer, and the regulations of the International Convention have to be followed. Mr. Preece estimated that a theoretical speed of nearly 63 letters per minute for the core of 650 lbs. copper and 400 lbs. gutta- percha would be reduced in practical working to 28 paying letters per minute. Mr. Lucas stated that a theoretical speed of 70 letters per minute for the same core was equivalent to four or five paying words a minute. Mr. Lamb, of the General Post Office, said that a deduction of 55 per cent. must be made from the theoretical to find the practical speed of a given cable. Mr. Ward, Manager of the Commercial Cable Company, calculated traffic; Mr. Carson, that a total allowance of 16 per cent. should be made for "dead of the Anglo-American Telegraph Company, 15 per cent.; and Mr. Gray, of the India-Rubber, Guita-Percha, and Telegraph Works Company, about 17 per cent. Mr. T. B. Ffinch, Director-in-Chief of the Indo-Europeau Telegraph Department of the Government of India and having charge of the telegraphs from Karachi
up the Persian Gulf and through Persia, stated that the average number of service indications which have to be forwarded with a message of 12 paying words of a length of eight letters each, would on the average be equivalent to 10 letters. Furthermore, he stated that the unavoidable use of the lines under his charge for administrative purposes would His estimate, therefore, of the total amount to less than 5 per cent. of the whole traffic. unavoidable "dead" traffic amounts to about 17 per cent.
By the theoretical speed of a cable the Committee understand the maximum number of words which can be transmitted in a minute, so that an experienced operator can certainly and easily read them. The practical speed is the proportion of that maximum number which remains after certain deductions have been made for the transmission of words for which no revenue is received and for loss of time.
28. The Committee ascertained that these deductions were made on account of—
1. Service indications and prefixes, such as station of origin, number of message, time, date, &c.
2. Repetitions, errors in transmission, corrections.
3. Necessary intervals between the messages, time lost by clerks, &c.
4. Administrative messages connected with the traffic.
There are, of course, other administrative messages which must necessarily be sent on the business of the line, but these could, in most cases, be left for periods when there was no traffic for transmission.
29. It must also be borne in mind, in considering this question, that though the speed of a cable is usually stated as being a certain number of words per minute, these In actual practice a word averages words are "reputed" words of five letters each. eight letters, the increase being due to the use of code words and to the omission of many conjunctions and prepositions when messages are sent “in clear.”
30. The so-called "words," however, which have to be added to each message as service indications and prefixes do not consist generally of more than two or three letters each.
31. After weighing all the evidence carefully, the Committee are of opinion that a deduction of 33 per cent. from the theoretical speed is amply sufficient to give the practical speed, or the paying traffic.
32. This estimate is a cautious one.
33. There is no apparent reason why, with good management, the "dead" traffic on
a Pacific cable should not be kept much nearer to the level which obtains on the Atlantic
REPORT.
than to that which obtains on the Eastern lines. In addition, however, must be taken into consideration unavoidable losses of time in each working hour, and the fact that the use of code words (usually long ones) is increasing.
34. It has also been stated in evidence that possibly a Pacific cable would have to comply with the regulations of the International Telegraph Convention, but in the case of a line touching only British territory this necessity may perhaps be avoided.
35. The estimate of 33 per cent, has been arrived at with the desire to include an allowance for every possible deduction from the earning power of the cable.
If the experience of the Atlantic Cable Companies can be relied on the percentage would be considerably reduced.
Number of Working Hours per Diem.—36. In this matter, again, the expert evidence was somewhat conflicting, but the Committee consider that an estimate of 18 hours A very per diem, during which the cable could be worked, would be a moderate one. small allowance for duplex working has been made in this calculation.
37. Duplex working is the system under which the same cable is made to transmit messages from both ends at the same time. It can be applied so as to add about 80 per cent, to the traffic sent by simplex working. But full advantage can only be taken of this system when the business hours are substantially the same at both ends of the cable. This, for instance, is the case between, say, London and Lisbon: as between London and New York, where the difference in point of time is about five hours, duplex is only regularly available for the few hours which may be considered part of the working day in both places: while as between this country and the east of Australia, where the difference is about ten hours, so that night here is almost synchronous with day there, duplex working would only be resorted to to a small extent.
38. The conclusion the Committee have arrived at is that the core of 552 lbs. copper and 368 lbs. gutta-percha might reasonably be expected to give 40 paying leiters a minute.
39. The core of 650 lbs. copper and 400 lbs. gutta-percha similarly would give 48 paying letters per minute.
40. To get the carrying capacity of these cables in a year the above numbers of letters should be multiplied by 60 (minutes to the hour); then by 18 (working hours per day); then by 300 (working days in a year). The totals on this basis would be :-
At 40 paying letters, or 5 paying words
At 48
**
or 6
11
-
-
1,620,000 words
1,944,000
41. Thus the lowest of these totals considerably exceeds the whole of the Australasian trallie in any year except 1895.
Cost of Laying-42. The India Rubber, Gutta-Percha, and Telegraph Works Com- pany has offered to lay the whole cable over the route recommended, with the first of the above-mentioned types for the long section, for the sum of 1,517,000l., this sum includ- ing the erection at each station of a suitable dwelling house and operating room, with duplicate sets of all proper instruments; also the use of two cable-repairing ships, with the cost of maintaining them as well as the cables themselves for three years.
43. This estimate included an allowance for 10 per cent. slack.
44. This allowance of slack is, in the opinion of the Committee, a reasonable one for actual laying, but they are of opinion that another 10 per cent, should be manufactured, which would be properly chargeable to the repair and maintenance fund to be herein- after mentioned.
45. The condition as to maintenance for three years was laid down by the Canadian Government in inviting tenders, but though there is some convenience in thus having maintenance guaranteed for the first three years, the Committee consider that such a period is unnecessarily long as a test of the original condition of the cable when laid, without being long enough to prove its durability while under water; and they would recommend that the contractors should be required to maintain the cable for six months.
⚫ 92683.
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PUBLIC RECORD OFFICE, LONDON
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