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

The New Anglo-Dutch Telephone Cable (1924)

Introduction: The 1924 Anglo-Dutch cable (UK - Netherlands 2) was made and laid by Siemens Brothers for the GPO, and incorporated several new technologies. It was the first Anglo-continental telephone cable to have more than four conductors, it used paper insulation and lead covering, and had shore-based vacuum tube amplifiers.

This article is from the October 1924 issue of The Telegraph and Telephone Journal, which was “Published monthly in the interests of the Telegraph and Telephone Service, under the patronage of the Postmaster-General”.

—Bill Burns

 

THE NEW ANGLO-DUTCH TELEPHONE CABLE.

The successful designing, construction, and laying of this cable marks a new era in telephony, which cannot but quicken the rate of progress and development of long-distance speech between this country and the continent of Europe. It may eventually show the way to sub-ocean speech under the Atlantic. As readers of this journal are aware, cables of this type have been actually laid, and are at present working under the Baltic, but the new Anglo-Dutch cable is the first lead-covered paper-insulated submarine telephone cable to be laid in tidal waters, which are also subject to strong and varied under-currents.

It is to the thermionic valve we must look for the key to the problem now solved. The valve made radical changes in telephone transmission, making good much of the line loss and reducing the need for heavy conductors to a figure which at one time would have appeared ridiculous.

This advantage is somewhat discounted, for while line losses are made good by the valve repeaters, the necessity for raising the standard of non-interference thereby becomes more clamant. The net result has, however, been a very definite reduction in the weight of the conductor.

Prior to the manufacture of the present telephone cable no Anglo-continental telephone cable has contained more than four conductors. The present cable contains four times this number, arranged in four groups, so that by superimposing it may ultimately prove possible to produce more than one dozen phantom circuits.

The new telephone cable between Holland and England being hauled ashore at Aldeburgh

The contractors, Messrs. Siemens Bros., Ltd., of Woolwich, appear to have provided for every contingency and to have spared neither money nor exacting care in the manufacture. New workshops and machinery were a necessity, even the iron wire used for the continuous loading of each conductor had to be “diamond-drawn” by special methods and a special form of heating had to be applied to ensure uniform permeability.

Paper-insulated and lead-covered cable has the distinct advantage of low electrostatic capacity plus a low leakance, a combination distinctly favourable to efficient speech transmission. The fact that the manufacturers were able to apply the lead coverings in unbroken lengths of ten nautical miles and to ship, lay, and land the total 82.3 nautical miles of cable without making a joint on board, was a very unusual performance. The total cable of 2,150 tons was carried and laid by the C.S. Faraday (2), the work commencing from Domburg, Walcheren, on the Dutch coast, and terminating at Aldeburgh, Suffolk, on Aug. 29 under good weather conditions.

Here are some of the principal features of the cable as laid down by the P.O. Engineering Department:

(a) Length 82.242 nautical miles.

(b) Number of conductors=16, in four sets of quadruple cores,

(c) Each conductor to be continuously loaded with iron wire.

(d) Dry paper insulation.

(e) Two separate lead coverings, with bituminous compound between them.

(f) Armouring of galvanised steel wires.

(g) Interference between circuits as measured on the standard cross-talk meter, using actual speech, cross-talk between physical circuits, not to exceed 400 millionths (equivalent to 75 miles of standard cable).

(h) Overhearing between a physical circuit and its associated phantom circuit not to exceed 4,000 millionths (equivalent to 52 miles of standard cable).

Of the tests taken after the entire cable was transferred to the cable steamer, the following should give some clear and definite indications of the high standard of efficiency reached:

In the same quad, maximum cross-talk, 200 millionths (equivalent to about 80 miles of standard cable).

Maximum overhearing, 2,000 millionths (equivalent to about 60 miles of standard cable).

Between quads, phantom to phantom, maximum 70 millionths (equivalent to 90 miles of standard cable).

J.J.T.

Last revised: 8 July, 2019

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