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Cordless Phones from British WWI Biplanes

Pilots during reconnaissance missions could quickly talk about received data by phone



The British Royal Flight Corps engineers developed such an air telephone.

As soon as people in the 18th century began to take off in balloons for the first time, military strategists immediately began to think about the seductive capabilities of aerial reconnaissance. Imagine the opportunity to notice the maneuvers of the enemy and his artillery from above - and even better if you had the opportunity to instantly transmit this information to your colleagues on earth. However, the technology of those years did not offer elegant solutions to such problems.

By the beginning of the 20th century, all the necessary components for the implementation of aerial reconnaissance appeared: telegraph, telephone and airplane. The problem was only to assemble them in a single device. Wireless enthusiasts were reluctant to meet government bureaucrats who tried not to spend money on financing untested technology.

During World War I, vital data was transmitted via wireless telegraph


In one of the early attempts, wireless telegraphy was used - sending telegraph signals over the radio. Its main drawback was size. The battery and transmitter weighed up to 45 kg and occupied a whole seat on the plane, and often there was no room for the pilot. An antenna in the form of a wire dangled behind an airplane, and before landing it had to be twisted. There was no place for a separate radio operator, so the pilot would have to do everything: observe the enemy, check the map, type in the coordinates in Morse code, and still fly the aircraft while under enemy fire.

Despite the difficulties, some pioneers were able to make this system work. In 1911, Lieutenant Benjamin Fualu, the pilot of the only U.S. Army aircraft, flew over the Mexican border and transmitted Morse code information to the communications troops located on the ground. Three years later, under the auspices of the Royal Flight Corps (KLK), Lieutenants Donald Lewis and Baron James tested the radio-telegraph communication between the aircraft, flying 16 km, and communicating with Morse code during the flight.

Quite quickly, the KLK wireless system first showed itself in business. On August 4, 1914, Britain entered the First World War. September 6th in flight during the Battle of Marnein France, Lewis noticed a 50-kilometer gap in the enemy’s positions. He sent a wireless message with a report of what he saw, after which the British and French attacked this gap. This was the first time that a wireless message was received from a British aircraft, and real measures were taken on its basis. The commanders of the British army instantly began to promote wireless communications, demand the supply of additional equipment and training pilots and ground support services.

Since then, formed in 1912 under the command of Captain Herbert Musgrave, KLK has grown rapidly. At first, Musgrave was uploaded with an investigation into a long list of war-related activities. The list included: launching balloons, kites, photographing, meteorology, bombing, shooting and communications. He decided to concentrate on the latter. At the beginning of the war, KLK took over the leadership of the Marconi experimental station at the Brooklands airfield in Surrey, southwest of London.


British intelligence biplane flies over enemy fortifications in France during World War I

In Brooklands in 1909, the first motor airplanes in England tore off the ground, although this place was not particularly suitable for the airport. The runway was right in the center of the racetrack, electric cables surrounded the field on three sides, and 30-meter-high brick pipes rose to the east.

At first, air reconnaissance pilots reported the effectiveness of artillery fire, suggesting directions. “A shortage of about 50 yards, a deviation to the right” - such a message once sent Lewis to Marne. Quite a long sentence for passing Morse code from the pilot's seat. By October 1914, the British had developed maps with a grid, so that using just a few numbers and letters, it was possible to designate both direction and distance (for example, A5 B3). But even after such simplification, wireless telegraphy remained an awkward affair.


The best solution seemed to be a direct voice message over a wireless telephone - only an open biplane cockpit didn’t quite facilitate conversations. Constant noise, vibration, air swirls - all this drowned out voices. Under constantly changing wind pressure, the facial muscles refused to maintain their shape. Even a crew member sitting a few centimeters from him could hardly understand the pilot, not to mention hearing the pilot speaking into the microphone on the radio, and even distinguishing his voice from background noise.

In the spring of 1915, Charles Edmond Prince was sent to Brooklands to lead the development of a bidirectional voice system for aircraft. Prince worked as an engineer with Marconi Co. since 1907, and he and the team, many of whose members also worked for Marconi, soon established an air-ground communication system.

The Prince's system did not at all resemble either modern smartphones or phones of the time. Although the pilot could talk to the ground station, the operator on the ground answered him only with Morse code. Another year was spent on the development of telephony, capable of transmitting voice from the ground to the plane and between planes.

Prince's group experimented with various microphones. In the end, they settled on a rather old version of the cone microphone with a thick diaphragm designed by Henry Hannings. Through trial and error, they found out the importance of testing the microphone outside the walls of laboratories and in typical flight conditions. They found that it was almost impossible to predict the behavior of a microphone in air during ground tests. As Prince later wrote about their design, “it is curious that on earth it seemed deaf and ineffective, but it showed itself very vigorously in the air.”

An important aspect was the material of the diaphragm. The team tested carbon, steel, hard rubber, celluloid, aluminum and mica. As a result, mica won - its natural frequency of oscillation was less affected by engine noise. After the war, Prince published the results of his research in 1920 in the journal Institution of Electrical Engineers.

Prince was one of the earliest supporters of electronic lamps, so his radio worked on lamps, not on crystals. However, the lamps that his team initially selected were terribly problematic and unreliable, so they had to sort out several different models. After the captain G.J. Round [one of the inventors of LEDs / approx. trans.], he began to design electronic tubes specifically for use in the air.

In the summer of 1915, the Prince group successfully tested the first air-to-ground voice communications using an airborne radiotelephone transmitter. Shortly afterwards, Captain J. M. Farnival, one of Prince's assistants, founded the Brooklands School of Wireless Education. Every week, 36 combat pilots trained through the use of a wireless apparatus and the art of correct articulation in the air passed through it. The school also trained officers in equipment maintenance.

Hands free calls using a laryngophone


But the Prince’s team did not stop there. In 1918, they released a pilot's helmet, in which telephones were built in around the ears, and a microphone in the throat area. A throat microphone ( laryngophone ) was wrapped around the neck to read vibrations directly from the pilot's throat - in this case, the background noise of the wind and the motor did not interfere. This significantly advanced communication, because it allowed pilots to talk “without hands,” or hands-free, as Captain B. S. Cohen wrote in his engineering report in October 1919.

By the end of the war, Prince and the engineers were able to provide air-to-ground, ground-to-air and air-to-air voice communications. The British Royal Air Force equipped 600 airplanes with voice-activated radio on undamped waves and opened 1,000 ground stations, employing 18,000 operators.

This example illustrates how military technology promotes innovation in wartime. However, keeping track of achievement history is sometimes quite difficult.

In a formal response to the 1920 Prince's work published in the IEE, Captain P.P. Eckersley noted that promoting airplane phones would be as difficult as developing them. He meant that Prince did not have an unlimited budget for research and development, so he had to first show the practical benefits of using air telephony.

In the description of the development, Prince was particularly proud that he and his team were able to demonstrate it to Lord Kitchener in St. Omer in February 1916, during the first demonstration of the practical use of the device.

However, Major T. Vincent Smith considered such a demonstration unreasonable. He served as a technical adviser to KLK, and argued that demonstrating a cordless telephone to senior officials would only inflame their imagination, and the commanders would decide that this device would solve all their important communication problems. Smith considered it his duty to stifle their enthusiasm in case he was asked to "do something impossible."

Round, the developer of electronic tubes, and Harry M. Dauset, chief test engineer at Marconi, add their refinements to the story of Prince. Round noted that studies of receivers and transmitters based on electron tubes began in 1913, even before the outbreak of war. Dausett said that it was necessary to pay tribute to the Marconi engineers who created the first working telephone (which only appeared with Prince in 1915).

In a 1920 article, Prince acknowledges that he did not include the full history of the invention, and that his contribution was to re-use existing schemes for use on airplanes. He pays tribute to the contributions of the Round and other engineers, as well as General Electric Co., which has patented a similar airborne telephony system used by US communications forces.

But such details rarely remain in history. Therefore, all the merits of creating an air telephone, which is now stored in the collection of the London Science Museum, are attributed only to Prince. Our task is to remember that this innovative apparatus was the result of the work of not one, but many people.

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