Radio control
The idea of controlling unmanned vehicles (for the most part in an attempt to improve the accuracy of torpedoes for military purposes) predates the invention of radio.
The latter half of the 1800s saw development of many such devices, connected to an operator by wires, including the first practical application invented by German engineer Werner von Siemens in 1870.
[2][3] At an 1898 exhibition at Madison Square Garden, Nikola Tesla demonstrated a small boat that used a coherer-based radio control.
[4] With an eye towards selling the idea to the US government as a torpedo, Tesla's 1898 patent included a clockwork frequency changer so an enemy could not take control of the device.
[5] In 1903, the Spanish engineer Leonardo Torres Quevedo introduced a radio based control system called the "Telekino"[6] at the Paris Academy of Sciences.
[12] In 1906, in the presence of an audience which included King Alfonso XIII of Spain, Torres demonstrated the invention in the Port of Bilbao, guiding the electrically powered launch Vizcaya from the shore with people on board, which was controlled at a distance over 2 km.
[14] In 1917, Archibald Low, as head of the secret Royal Flying Corps (RFC) experimental works at Feltham, was the first person to use radio control successfully on an aircraft, a 1917 Aerial Target.
[18] In 1922 he installed radio control gear on the obsolete US Navy battleship USS Iowa so it could be used as a target ship[19] (sunk in gunnery exercise in March 1923).
This was a remotely controlled unmanned version of the de Havilland "Tiger Moth" aircraft for Navy fleet gunnery firing practice.
However, by the end of the war, the Luftwaffe was having similar problems attacking Allied bombers and developed a number of radio command guided surface-to-air anti-aircraft missiles, none of which saw service.
The effectiveness of the Luftwaffe's systems, primarily comprising the series of Telefunken Funk-Gerät (or FuG) 203 Kehl twin-axis, single joystick-equipped transmitters mounted in the deploying aircraft, and Telefunken's companion FuG 230 Straßburg receiver placed in the ordnance to be controlled during deployment and used by both the Fritz X unpowered, armored anti-ship bomb and the powered Henschel Hs 293 guided bomb, was greatly reduced by British efforts to jam their radio signals, eventually with American assistance.
The German development teams then turned to wire-guided missiles once they realized what was going on, but the systems were not ready for deployment until the war had already moved to France.
The German Kriegsmarine operated FL-Boote (ferngelenkte Sprengboote) which were radio controlled motor boats filled with explosives to attack enemy shipping from 1944.
Both the British and US also developed radio control systems for similar tasks, to avoid the huge anti-aircraft batteries set up around German targets.
Multi-channel developments were of particular use to aircraft, which really needed a minimum of three control dimensions (yaw, pitch and motor speed), as opposed to boats, which required only two or one.
As the electronics revolution took off, single-signal channel circuit design became redundant, and instead radios provided proportionally coded signal streams which a servomechanism could interpret, using pulse-width modulation (PWM).
More recently, high-end hobby systems using pulse-code modulation (PCM) features have come on the market that provide a computerized digital data bit-stream signal to the receiving device, instead of the earlier PWM encoding type.
