Remote control

In electronics, a remote control is an electronic device used to operate the device from a distance, usually wirelessly. For example, in consumer electronics, a remote control can be used to operate devices such as a television set, DVD player or other home appliance, from a short distance. A remote control is primarily a convenience feature for the user, and can allow operation of devices that are out of convenient reach for direct operation of controls. In some cases, remote controls allow a person to operate a device that they otherwise would not be able to reach, as when a garage door opener is triggered from outside or when a Digital Light Processing projector that is mounted on a high ceiling is controlled by a person from the floor level. Early television remote controls (1956–1977) used ultrasonic tones. Present-day remote controls are commonly consumer infrared devices which send digitally-coded pulses of infrared radiation to control functions such as power, volume, channels, playback, track change, heat, fan speed, or other features varying from device to device. Remote controls for these devices are usually small wireless handheld objects with an array of buttons for adjusting various settings such as television channel, track number, and volume. For many devices, the remote control contains all the function controls while the controlled device itself has only a handful of essential primary controls. The remote control code, and thus the required remote control device, is usually specific to a product line, but there are universal remotes, which emulate the remote control made for most major brand devices. Remote control in the 2000s includes Bluetooth connectivity, motion sensor-enabled capabilities and voice control. In 1894, the first example of wirelessly controlling at a distance was during a demonstration by the British physicist Oliver Lodge, in which he made use of a Branly's coherer to make a mirror galvanometer move a beam of light when an electromagnetic wave was artificially generated. In 1895, Jagadish Chandra Bose demonstrated radio waves by triggering a gun and sounding a bell using microwaves transmitted over a distance of 75 feet through intervening walls. Radio innovators Guglielmo Marconi and William Preece, at a demonstration on December 12, 1896, at Toynbee Hall made a bell ring by pushing a button in a box that was not connected by any wires. In 1898 Nikola Tesla filed his patent, U.S. Patent 613,809, named Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles, which he publicly demonstrated by radio-controlling a boat during an electrical exhibition at Madison Square Garden. Tesla called his boat a 'teleautomaton'. In 1903, Leonardo Torres Quevedo presented the Telekino at the Paris Academy of Science, accompanied by a brief, and making an experimental demonstration. At the same time, he obtained a patent in France, Spain, Great Britain, and the United States. The Telekino consisted of a robot that executed commands transmitted by electromagnetic waves. With the Telekino, Torres-Quevedo laid down modern wireless remote-control operation principles and was a pioneer in the field of remote control. In 1906, in the presence of the king and before a great crowd, Torres successfully demonstrated the invention in the port of Bilbao, guiding a boat from the shore. Later, he would try to apply the Telekino to projectiles and torpedoes but had to abandon the project for lack of financing. The first remote-controlled model airplane flew in 1932, and the use of remote control technology for military purposes was worked intensively during the Second World War, one result of this being the German Wasserfall missile. By the late 1930s, several radio manufacturers offered remote controls for some of their higher-end models. Most of these were connected to the set being controlled by wires, but the Philco Mystery Control (1939) was a battery-operated low-frequency radio transmitter, thus making it the first wireless remote control for a consumer electronics device. Using pulse-count modulation, this also was the first digital wireless remote control. The first remote intended to control a television was developed by Zenith Radio Corporation in 1950. The remote, called 'Lazy Bones,' was connected to the television by a wire. A wireless remote control, the 'Flashmatic,' was developed in 1955 by Eugene Polley. It worked by shining a beam of light onto one of four photoelectric cells, but the cell did not distinguish between light from the remote and light from other sources. The Flashmatic also had to be pointed very precisely at one of the sensors in order to work. In 1956, Robert Adler developed 'Zenith Space Command,' a wireless remote. It was mechanical and used ultrasound to change the channel and volume. When the user pushed a button on the remote control, it struck a bar and clicked, hence they were commonly called a 'clicker,' but it sounded like a 'clink' and the mechanics were similar to a pluck. Each of the four bars emitted a different fundamental frequency with ultrasonic harmonics, and circuits in the television detected these sounds and interpreted them as channel-up, channel-down, sound-on/off, and power-on/off. Later, the rapid decrease in price of transistors made possible cheaper electronic remotes that contained a piezoelectric crystal that was fed by an oscillating electric current at a frequency near or above the upper threshold of human hearing, though still audible to dogs. The receiver contained a microphone attached to a circuit that was tuned to the same frequency. Some problems with this method were that the receiver could be triggered accidentally by naturally occurring noises or deliberately by metal against glass, for example, and some people could hear the lower ultrasonic harmonics.