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

1976 TAT-6

The sixth in a series of transatlantic telephone cables which began with TAT-1 in 1956, TAT-6 was laid in 1976 between South Kingstown, Rhode Island, and Saint-Hilaire-de-Riez, Vendée, France. TAT-6 had a capacity of 4,000 telephone circuits. It was withdrawn from service in 1994.

The system was developed as a joint project of AT&T, the British Post Office, and the French Telecommunications Ministry.

AT&T (Bell Laboratories) was given the development responsibility for the following portions of the system: repeaters and devices for repeaters, repeater factory test sets, laying test sets, couplings and junction boxes, ocean-block equalizers, supervisory tone and repeater monitoring test set, shipboard and shore high-voltage power-feeding equipment, and order wire equipments for cable laying and burying.

The British Post Office was given the development responsibility for cable, jointing methods, cable handling procedures, cable fault location test sets, cable factory test sets, and other associated test equipment.

The French Ministry for Posts and Telecommunicaions was given the development responsibility for the terminal transmission equipment (multiplex and wide-band line) between the supergroup distribution point and the transmission equipment side of the power separating filter, the order wire and associated terminal signaling equipment, and maintenance test sets.

The type SG cable system was 3,396 nautical miles with repeater spacing of 5.1 nautical miles. The manufacture of the cable was divided as follows: Standard Telephones & Cables Ltd 2400 nm.; Simplex Wire & Cable Co 95 nm.; Câbles de Lyon 1200 nm. The deep sea portion, some 3,000 nautical miles km) in length, was laid by AT&T’s cableship Long Lines. The shore end were laid by CS Vercors.

Site visitor Ed Haemmerle worked for AT&T from 1966 to 1998 as an engineer, spending about 25 of those years at AT&T’s repeater manufacturing facility in Clark, NJ. He worked on SF, SG, and SL systems, and also on the SF Equalizer.

Ed provided this photograph of the first SG repeater for the TAT-6 system; he is second from left in the front row:

1st SG Repeater
For TAT-6 System
Green Hill, Rhode Is. to St. Hilaire, France
4,000 Channel 30 MHz System
5.1 Nautical Mile Spacing
796 Units Required

This route map of the cable is engraved on the marble base of a commemorative desk pen issued to mark the dedication of TAT-6 in September 1976:


References: Bell System Technical Journal 57: 7. September 1978: SG Undersea Cable System (a series of technical articles on TAT-6)

Last revised: 3 January, 2016

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