Cybernetics is the science and application of implanting machines and other devices in a living body. Although the types of devices implanted are varied, the reason is usually to replace or enhance the body's natural functions, or to provide convenient access to frequently used tools. Similar to drugs and alcohol, a little here and there is considered normal, but trying to meet or exceed your Cybernetic Tolerance is considered to be unhealthy. Some common devices that are implanted are: communicators, replacement organs or limbs, tradesman tools (sonic screwdrivers, laser welders, etc).
The field of cybernetics is as varied as technology itself. If it can fit on or in the body, you can bet that someone has had it cybernetically implanted. With all of this variation though, there are some things all cybernetic implants have in common.
Most if not all cybernetics are linked to the brain. One can activate almost any function just by thinking about it. Cheaper implants, or those with complicated functions may require some manual configuration. It should be noted that if a user has an incomplete or incorect function list, they may not be able to access those functions just by thinking about them.
Cybernetics are best considered tools, rather than replacements for the real thing. Like all tools, they require training and practice in their use. A person may have been using legs all of their life, and still have to learn to walk again if both legs are replaced with implants. Like any other technology someone can only make their cybernetics do things they understand how to do with the given tools. A new limb capable of more precise movement than the original will not automatically grant the user more precise movements.
Cybernetics have an unnatural feeling when they are implanted in or grafted to ones body. There is no sensation of being "one" with the new parts even though the functions are linked to the brain. The body often tries to reject them as it would with any foreign objects, and the brain has difficulty accepting the new parts as anything other than new tools. More expensive devices can have transmitters that help the body and brain ingore these issues, but they are less than perfect, and without proper configuration by a cybernetics specialist may make things worse. For that reason, these devices are often custom made for each person, and for each implant. Over time, typically many years at least, an individual will become accustomed to their cybernetic implants and comfortable with their use, but they never take on the sensation of being natural body parts.
With the exception of sensory replacement implants, most cybernetics do not process a full and proper sensory range. This is especially disconcerting to those with replacment hands (or whole arms). While advanced pressure sensors keep them from -for example- caressing a loved one too hard by accident, the tactile feed back is very different. The tactile feedback is usually described as "cold" or "sterile" like the implants themselves. Very complicated set ups involving some organic, and some mechanical components are capable of providing more natural feed back.
All implants require a power source. Since most people only have one or two, most implants have a little "jack" that pokes through the skin. This jack hooks up to a charging unit which is usually located next to someone's bed. Charging is usually painless, though a very cheap, or malfunctioning implant might tingle a bit during the charging process. People with more complicated implants may require more complex power sources, and/or charging units. Some very simple implants can take energy directly from the body.
Unless the implant is small, it can be difficult and expesnive to disguise an implant as natural. This is especially true of replacement limbs. In the spirit of making a virtue out of things that can't be avoided, many find comfort expressing themselves with decorative decals and paint jobs, or shiny chrome plating.
Cybernetic implants are like any other mechanical device: they require maintenance. Most individuals who have chosen to live with cybernetic implants train themselves to be able to perform basic maintenance on their own, although they usually need to visit a cybernetics specialist if their implants malfunction. The failure rate of an implant is usually proportional to its complexity. Very simple implants without moving parts, such as sensory enhancements, usually last a lifetime, while mechanically complex implants that receive wear and tear, such as limb replacements, must usually be maintained on a regular schedule.
Another consideration that must be given when receiving an implant is the biological impact of the implant on the body. For example, having one arm replaced by a heavy tool will ruin the body's balance, and over time can lead to muscle strain and even bone deformities. Even if the heavy arm tool were counterbalanced, the additional weight would put strain on the spine and back muscles, and could eventually lead to a chronic condition. Unscrupulous cyberneticists might overlook these issues and leave their patients to deal with them later on when they become a problem, but a good cyberneticist considers the overall impact of their work, and will take additional measures to ensure that long-term consequences of the implant work are mitigated. (Note that these are separate issues from Cybernetic Tolerance, which is a more general measure of the body's ability to adapt to cybernetic implants.)
There are two basic types of cybernetic implants: replacements and enhancements.
Replacements are usually used when a natural body part, such as a limb or organ, fails to perform adequately, or is damaged or destroyed. Cybernetic replacements are usually designed to operate at the same level as the parts they replace, and typically try to match the original part's physical weight, dimensions and surface appearance (if visible outside the body) as well. The match is rarely perfect and never holds up to close scrutiny, so some individuals will instead embrace the mechanical appearance of their replacements (see Appearance above).
Cybernetic enhancements, on the other hand, are intentionally designed to try to exceed the performance of original body parts, or try to add functions that the original parts did not possess. This can include improved senses, improved limb strength or speed, added tools, or anything else which can practically be mounted on or within the body. Unlike cybernetic replacements, which are usually used to help a being recover from an accident or illness, cybernetic enhancements are usually either chosen voluntarily by the subject, or forced upon them by a higher authority, such as a military commander or a judge. Because cybernetic enhancements are unlike natural body parts by design, they also incur a greater cost to an individual's Cybernetic Tolerance.