A huge structure, once the most powerful telegraph transmitter in the world, is due to arrive at Wroughton Science Museum today.

The copper tuning coil, which is 11 metres high and eight metres long, is being donated by telecommunications firm BT.

It was used in the development of the country's telephone and radio system in the 1940s.

The structure, which consists of six copper coils and is supported by a wooden frame, once stood at Rugby Radio Station, in the Midlands, and was used to tune antennas to the right frequencies.

The original was destroyed by fire in 1943 but was quickly replaced because of its huge importance to the war effort.

At the time, it carried communications with the Royal Navy and other shipping and with the French Resistance.

Its importance continued into the Cold War when secret information was transmitted to ships and submarines. It was was finally decommissioned in March 2003.

It is due to go on display at the museum in the spring.

David Hay, the head of corporate memory at BT, said: "This is a fascinating and historic piece of telecommunications apparatus, part of the equipment which was once the hub of the UK's international communications system.

"We felt it was crucial to preserve it for future generations so that they can learn about its once vital function in the country's communication infrastructure."

The museum is part of a UK-wide range of museums and exhibitions in the Connected Earth network displaying BT's heritage.

Mr Hay added: "There is an earlier link with Wroughton as the original receiving station for the early transatlantic telephone service, operated from Rugby Radio Station, was built there."

John Liffen, the curator of communications at the science museum, said: "The Rugby Tuning Coils are a wonderful, almost monumental reminder of worldwide radio communications in their early pioneering days."

Factfile

The device itself will be arriving in Wroughton on the back of a low-loader.

The coil was built at Rugby Radio Station, as part of the Government's interest in developing powerful radio transmitters that would link the-then vast empire by radio.

During the Second World War many of Rugby Radio Station's transmitters were used by the Armed Forces.

At its launch the station was the most powerful in the world. It first transmitted in Morse code on 16kHz with an aerial power of 350kW.

The tuning coil frame was built using American whitewood, and fixed with wooden bolts. Some were later replaced with nylon bolts to provide insulation and support for the copper.

These materials ensured energy loss was kept to a minimum. For the same reason, the use of steel girders in constructing the radio station that housed the tuning coil was restricted as much as possible.

Now there is little use for the coil as its role has been taken over by orbiting satellites.

Anthony Osborne