TAT-1 Opens a New Era in Transatlantic Communication

On 25 September 1956, TAT-1, the first submarine transatlantic telephone cable system, entered service. Linking Scotland and Newfoundland, it provided a more dependable way to carry telephone conversations between Europe and North America.

Voices Across the Ocean

Transatlantic telephone calls were already possible before TAT-1. A commercial radio service between Britain and the United States had opened in 1927, but its connections were vulnerable to atmospheric interference and changing radio conditions.

Telegraph cables had crossed the Atlantic since the nineteenth century, carrying written messages. Transmitting speech beneath the ocean presented a different technical challenge: electrical signals needed reliable amplification throughout their long underwater journey.

An International Engineering Achievement

TAT-1 was developed through cooperation between the British Post Office, AT&T and Bell Laboratories, and the Canadian Overseas Telecommunications Corporation.

Its main ocean link ran from the Oban area of Scotland to Clarenville, Newfoundland. Further connections carried calls onwards through the North American and European telephone networks.

The Atlantic crossing used two cables, one for each direction of transmission. Submerged repeaters amplified the signals along the route. These devices had to withstand deep-ocean conditions and operate reliably for years, since repairs would be difficult and expensive.

The cable ship Monarch laid the main Atlantic cables during the summers of 1955 and 1956, turning years of research and planning into a working communications link.

Thirty-Six Channels Connect Two Continents

The system opened with a capacity of 36 telephone channels. Its inauguration brought together participants in London, New York and Ottawa in a conversation demonstrating the new connection.

That capacity may seem modest today, but it represented a major advance. The cable offered greater reliability than the existing radio links and helped meet growing demand for international calls.

A Foundation for Future Networks

TAT-1 remained in service until 1978. Its success demonstrated that complex electronic equipment could function dependably on the ocean floor for decades.

The opening of TAT-1 did not mark the first time people spoke across the Atlantic. It marked the arrival of a reliable underwater telephone connection, an important step towards the submarine communications networks that would follow.