Transparency (telecommunication)
In telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

s, transparency can refer to:
  1. The property of an entity that allows another entity to pass through it without altering either of the entities.
  2. The property that allows a transmission system
    Transmission system
    In telecommunications a transmission system is a system that transmits a signal from one place to another. The signal can be an electrical, optical or radio signal....

     or channel
    Channel (communications)
    In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...

     to accept, at its input, unmodified user information
    User information
    User information is information transferred across the functional interface between a source user and a telecommunications system for delivery to a destination user.In telecommunications systems, user information includes user overhead information....

    , and deliver corresponding user information at its output
    Output is the term denoting either an exit or changes which exit a system and which activate/modify a process. It is an abstract concept, used in the modeling, system design and system exploitation.-In control theory:...

    , unchanged in form or information content. The user information may be changed internally within the transmission system, but it is restored to its original form prior to the output without the involvement of the user.
  3. The quality of a data
    The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...

     communications system
    Communications system
    In telecommunication, a communications system is a collection of individual communications networks, transmission systems, relay stations, tributary stations, and data terminal equipment usually capable of interconnection and interoperation to form an integrated whole...

     or device that uses a bit
    A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

    -oriented link protocol
    Link protocol
    In communications, a link protocol is a method and specification for transmission of data from one node on a local network or network link to another node on the same link...

     that does not depend on the bit sequence
    In mathematics, a sequence is an ordered list of objects . Like a set, it contains members , and the number of terms is called the length of the sequence. Unlike a set, order matters, and exactly the same elements can appear multiple times at different positions in the sequence...

     structure used by the data source.

Some communication systems are not transparent.
Non-transparent communication systems have one or both of the following problems:
  • user data may be incorrectly interpreted as internal commands. For example, modems with a Time Independent Escape Sequence
    Time Independent Escape Sequence
    The Time Independent Escape Sequence, or TIES, was a short-lived modem standard invented to avoid a patent held by Hayes Microcomputer Products...

     or 20th century Signaling System No. 5
    Signaling System No. 5
    CCITT5 was a multi-frequency telephone signalling system in use from the 1970s for International Direct Distance Dialing . It was sometimes nicknamed "Atlantic Code" because the first IDD connections between Europe and North America used it....

     and R2 signalling
    R2 signalling
    R2 is a 1950s- and 1970s-era channel-associated-signalling signalling protocol used outside of the former Bell System to convey information along a telephone trunk between two telephone switches in order to establish a single telephone call along that trunk....

     telephone systems, which occasionally incorrectly interpreted user data (from a "blue box") as commands.
  • the output "user data" may not always be the same as the input user data. For example, many early email systems were not 8-bit clean
    8-bit clean
    8-bit clean describes a computer system that correctly handles 8-bit character sets, such as the ISO 8859 series and the UTF-8 encoding of Unicode.- History :...

    ; they seemed to transfer typical short text messages properly, but converted "unusual" characters (the control characters, the "high ASCII" characters) in an irreversible way into some other "usual" character. Many of these systems also changed user data in other irreversible ways – such as inserting linefeeds to make sure each line is less than some maximum length, and inserting a ">" at the beginning of every line that begins with "From ". Until 8BITMIME, a variety of binary-to-text encoding techniques have been overlaid on top of such systems to restore transparency – to make sure that any possible file can be transferred so that the final output "user data" is actually identical to the original user data.
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