History of the Atlantic Cable & Undersea Communications
from the first submarine cable of 1850 to the worldwide fiber optic network

Traffic on the Transatlantic Telephone Cable
during its First Four Weeks in Service (1956)

Introduction: The 1956 opening of the first transatlantic telephone cable system, TAT-1, marked the beginning of the modern era of cable communications. The cable opened for service on 25 September 1956, and this article gives some details of the volume of traffic over the next four weeks.

It's interesting to note that two of the six Canadian voice channels were used to provide eleven telegraph (Telex) circuits which supplemented (and eventually replaced) the existing transatlantic wireless circuits and telegraph cables. Additionally, seven of the thirty circuits between New York and London were used for direct connections from the USA to Germany (two), France, Belgium, Holland, Switzerland, and Denmark (one each).

The article was first published in The Post Office Electrical Engineers’ Journal, January 1957, and is reproduced here by kind permission of The Institute of Telecommunications Professionals.

—Bill Burns

Traffic on the Transatlantic Telephone Cable during its First Four Weeks in Service
A.G. Sutherland

The transatlantic telephone cable was brought into public use at 6 p.m. on the 25th September, 1956, when 22 of the cable circuits [from London] to the United States and six circuits to Montreal were put into service. Public response was most marked, and although normal business hours had already passed, 260 calls were connected on that night. No difficulty was experienced in handling the traffic and calls were readily cleared on demand. During the first 24 hours of public service 588 calls were exchanged between London and the United States and 119 with Canada.

Some of this was probably curiosity traffic which arose from the broadcasts of the formal opening of the cable, and while the traffic fell away a little at first from the high figures recorded, it soon recovered. The average number of calls made daily with the United States over the first few weeks of cable service amounted to 510, an increase of 55 per cent over the average of 330 calls per day which obtained before the opening of the cable. On the service with Canada the average daily total over the same period was 156 calls, an increase of 100 per cent over the daily average of 76 calls obtained previously on radio channels. World events in early November caused material increases in traffic and 683 calls were recorded with the United States on the 8th November and 302 calls with Canada on the 4th November.

The increase in the outgoing traffic has been more pronounced in the full-rate period and this suggests that business people are making more use of the service. A marked feature on the Montreal route is the large increase in calls incoming to the United Kingdom and in particular of those routed via London to the continent of Europe. In addition to the increase in the number of calls there has also been an increase in the average paid time per call.

All the cable circuits were kept in service up to the 15th October, while some of the radio channels, retained as a standby, were used for reports and service correspondence only. But after the first three weeks, radio circuits were brought into use again for traffic when they were of a sufficiently high standard.

The facilities offered by the cable have been welcomed by the public and many favourable comments have been made about the quality of transmission on the circuits. The reliability of the cable circuits has also had an effect on the percentage of completed calls. During the three weeks immediately preceding the opening of the cable, when radio conditions were reasonably good, the percentage of completed calls varied from 71 to 81 per cent on the New York route and from 81 to 85 per cent on the Montreal route. In the three weeks that followed the opening of the cable circuits the percentage varied from 85 to 89 on the New York route and from 88 to 92 per cent on the Montreal route.

Two of the telegraph channels to Canada provided by the transatlantic telephone cable are in service at Electra House to supplement the facilities given by the existing wireless telegraph circuits and the submarine telegraph cables with Canada. The Canadian Overseas Telecommunications Corporation has installed a telex switchboard in Montreal and international telex service was made available to telex subscribers in Canada early in December over the telegraph circuits in the transatlantic telephone cable. Certain of the Montreal telegraph channels will be connected to the teleprinter automatic switching network (for strictly limited use) early in the New Year.

Last revised: 14 May, 2017

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