The document summarizes the history and development of transatlantic telecommunications cables. It discusses early failed attempts to lay a cable across the Atlantic in the 1850s and 1860s. The first successful transatlantic cable, called TAT-1, was laid between Scotland and Newfoundland between 1955-1956. Technological advances like coaxial cable, polyethylene insulation for the cable, and reliable vacuum tubes allowed for underwater signal amplification. TAT-1 initially carried 36 telephone channels when it was inaugurated in 1956.

1. Further attempts of Telegraph
Cable
On 3 September, 1858, the cable failed.
Reason:
In an attempt to increase the speed of
transmission,
the voltage on the line was boosted from
600V to 2,000V,
and the insulation on the cable couldn't cope.

2. Great Eastern
• The new cable was laid by the ship Great
Eastern captained by Sir James Anderson. Ship
was fitted with three iron tanks for the reception
of 4,300 km of cable, and decks were furnished
with the paying-out gear.
• On July 13, 1866, Great Eastern started paying
out despite problems with the weather.
• On the evening of Friday, July 27, the expedition
reached the port of Heart's Content in a thick
fog.

4. Laying cable by ship

5. Transatlantic Telecommunications
Cable
• Was discussed in 1920s.
• But to be practical it needed a number of
technological advances which did not arrive until
the 1940s.
• TAT-1(Transatlantic No. 1) was the first
transatlantic telephone cable system. It was laid
between Gallanach Bay, near Oban, Scotland
and Clarenville, Newfoundland between 1955
and 1956 by the cable ship Monarch.
• It was inaugurated on September 25, 1956,
initially carrying 36 telephone channels.

6. Initial Stages of Project
• The agreement to make the connection
was announced by the Postmaster
General on December 1, 1953.
• The project was a joint one between the
General Post Office of the UK, the
American Telephone and Telegraph
company, and the Canadian Overseas
Telecommunications Corporation

7. (contd.)
• The developments that made TAT-1
possible were coaxial cable, polyethylene
insulation (replacing gutta percha), very
reliable vacuum tubes for the submerged
repeaters and a general improvement in
carrier equipment.
• Transistors were not used, being a recent
invention.

8. TAT-1

9. Small vacuum tubes that could
operate under water
These could operate under water for 20 years
or more meant that amplifiers could be buried
at sea with the cable.

10. Project Summary
• There were to be two main cables, one for each direction
of transmission.
• Each cable was produced and laid in three sections, two
shallow-water armored sections, and one continuous
central section 2,800 km long.
• The electronic repeaters were designed by the Bell
Telephone Labs of the US and they were flexible and
were inserted into the cable at 69 km intervals - a total of
51 repeaters in the central section.
• The armored cables were manufactured southeast of
London, at a factory in Erith, Kent, owned by Submarine
Cables Ltd.