There are many ways to transmit information. The main categories are optical, audible, electronic, olfactory, and tactile. The art and science of Information and Communication Technology deals with the ways that data can transfer from one entity to another. Data transmission can be as simple as waving your hand in a crowd to let your friend know where you are. In some cases, the data converted into one meduim, transmitted, and then converted back into data at the far end. In others, the data stays in its original format from point of origin to recipient.

Examples of optical communication include (in general order of complexity):

  • Signage A surface with the message written on it. Depending on the size and location, they can be seen for quite a distance, and convey messages from warnings (Do not dredge here) to advertisements (Buy Burma Shave). The printed page is one of the most prevalent types of optical data transmission. Smoke signals are another form of signage. So is a television screen or a computer monitor. How that information gets there is another aspect of the technology.
  • Semaphore This is a method of communication where flags are used to transmit information a great distance. The message in alphabet form is sent using two flags held in various positions by an operator to designate each letter. The recipient notes the flag positions and translates the message back into text. Once used to a great extent (Napoleon had semaphore towers built across Europe to rapidly send messages) this method of data transmission has fallen out of use, although it is still practiced by history buffs and Boy Scouts.
  • International maritime signal flags. These are flags that have specific meanings, from letters and numbers to messages (actually a form of signage.) Some flags like the Blue Peter (A blue flag with a white square in the center) have different meanings in port and at sea. In the Blue Peter’s case in port it means, “all aboard, vessel is about to proceed sea” and at sea it means, “your lights are out or burning badly”. They are still used today.
  • Symbols Another form of signage, a symbol is an agreed-upon configuration that represents a specific message. Often the symbolism is drawn from actions that were previously related to the concept involved. The "circle and bar" negative symbol that one finds on no smoking signs and other prohibitive notification messages stems from the depiction of an arm reaching across the body for a weapon, for example. Symbols can also be very complex, in the case of crests, coats of arms, and other heraldric devices that inform the observer about the family lineage of the owner.
  • Signal lights Lights can be used to transmit information in a variety of ways. One can use the number of lights visible to convey a message (one if by land or two if by sea, and I on the opposite shore will be), or one can flash (or cover and uncover) the light in sequence to send code. This method was heavily used on land until the advent of radio and at sea and with the military to some extent to this day (radios tended to be less reliable in the harsh environment of the sea, and in combat lights can’t be easily intercepted by the enemy.)
  • Laser transmission A direct descendant of the signal light, laser transmission simply requires more advanced equipment to send, receive, and decode the transmission. The data is encoded and sent via a beam of coherent light to the target. In (relatively) short-range line-of-sight (LOS) applications, the beam can simply be sent through the air, but for really long distances and non LOS applications such as data networking in a building, fiber-optic lines made of glass or plastic “carry” the laser beams to their target around corners and under or over obstacles.

Audible data transmission can be as simple as speaking to someone, or clapping your hands to let someone know you appreciate their performance.

  • Bells and whistles Alarm bells and emergency sirens are audible signals, and inform the listener not only because of their shrill tones, but their staccato rhythm as well. A phone ringer, an audible prompt on a switch, and a doorbell are also examples.
  • Coded tones Morse code is usually thought of when one thinks of coded sound (although it can also be sent optically as flashes of light and dots and dashes on paper tape) and almost everyone knows the tones that spell out the international distress signal SOS (short-short-short, long-long-long, short-short-short). Secret knocks (shave-and-a-hair-cut, two-bits!) and the stereotypical native drums in the jungle are other examples.
  • Speech ‘Nuff said (pun intended.)

Data can be encoded and sent electromagnetically. The method of encoding can be analog or digital.

  • Wires Telegraph, Fax, traditional telephones, and many computer peripherals use wires to transmit data from one place to another. This data can take the form of any of the other methods of transmission, such as information on a screen, sound from a phone, or printed paper from a fax. The data can also be direct as in electric shocks delivered to a subject (just being thorough here) to communicate displeasure or to train an animal.
  • Wireless The data can also be transmitted through the air via radio, and converted to standard electromagnetic media upon reception. Relays on the ground or in space on board a satellite retransmit signals until they reach their destination.
Olfactory signals are usually transmitted as a side effect of other actions, but may be sent deliberately.
  • Pheromones All animals emit odors. These odors send a great deal of information, and the amount of information transmitted depends upon the species (and sometimes the sex) of the recipient. Humans tend to ignore their odors, but the information is there. It has been clinically proven that people who make good matches due to the potential immunity spectrum in their offspring like one another’s smell. Other examples include dogs sniffing one another (they have scent glands in their hind legs) and cats rubbing against your legs (they are marking you with glands in their shoulders.)
  • Smell Flowers smell good to inform bugs they are hot for sex. (see pheromones) Edible plants smell good too, and other materials suitable for consumption emit pleasant smells, sometimes in the process of preparation. Bad smells are usually warnings, and some animals such as skunks have learned to use a terrible odor as a weapon.
  • Scents I separate scents from smell to differentiate between natural and artificial odors. Manufacturers add scent to their products to convey messages. Cleansers smell that way mostly because people want the stuff they clean to smell a certain way to let them (and their visitors) know it has been cleaned recently. The scent usually came from a natural substance that performed that task that an artificial product now performs, or a sweet smell that connotes the impression of something fresh. Poisons are often scented to smell bad as a warning, like the "rotten eggs" smell given to cooking gas to warn of a leak.
The sense of touch is also an important conveyor of information.
  • Bumps and ridges Braille is an alphabet made up of raised bumps in specific arrangements to enable the blind to read with their fingertips. The bumps can be embossed in materials ranging from paper to metal, and can even be used to deliver computer-generated content with an array of pins that rise and fall in patterns to present Braille characters. (Louis Braille was a Frenchman who lost his sight as a result of running with a leather awl (long and pointy) as a child, so your mother was right.) Many keyboards and keypads have reference bumps on the “f”, “j” and “5” to give the user a finger-positioning reference without their having to look.
  • Textures How smooth or rough a surface is can also convey information. Here again, manufacturers will use the texture of a surface to convey impressions of quality, ruggedness, or sexuality in a product. The sides of many roads have rows of little ruts to create a vibration in the wheels of a car straying off the path to waken the driver (the main reason cars drift off the road.) This leads to…
  • Bumps and vibration many devices now use vibration to deliver a message, from “you have a phone call” to “the batteries in your Segway are dying”. This is usually an alert message to either reinforce or replace an audible alarm or notification. Some devices deliver bumps or taps to convey numbers or code.

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