telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...

s, ''transparency'' can refer to: #The property of an entity that allows another entity to pass through it without altering either of the entities. #The property that allows a transmission system or channel to accept, at its input, unmodified

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 inform ...

, and deliver corresponding user information at its output, 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. #The quality of a

data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...

communications system A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interoperat ...

or device that uses a bit-oriented link protocol that does not depend on the bit

sequence In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is called ...

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 The Time Independent Escape Sequence, or TIES, is a modem protocol standard invented to avoid a patent held by Hayes Microcomputer Products. TIES is an escape sequence that switches the modem from "data mode" to "command mode", allowing instructions ...

or 20th century

Signaling System No. 5 The Signaling System No. 5 (SS5) is a multi-frequency (MF) telephone signaling system that was in use from the 1970s for International Direct Distance Dialing (IDDD). Internationally it became known as CCITT5 or CC5.

and R2 signalling telephone systems, which occasionally incorrectly interpreted user data (from a "

blue box A blue box is an electronic device that produces tones used to generate the in-band signaling tones formerly used within the North American long-distance telephone network to send line status and called number information over voice circuits. ...

") as commands. * output "user data" may not always be the same as input user data. For example, many early

email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...

systems were not 8-bit clean; they seemed to transfer typical short text messages properly, but converted "unusual" characters (the

control character In computing and telecommunication, a control character or non-printing character (NPC) is a code point (a number) in a character set, that does not represent a written symbol. They are used as in-band signaling to cause effects other than the ...

s, the "

high ASCII Extended ASCII is a repertoire of character encodings that include (most of) the original 96 ASCII character set, plus up to 128 additional characters. There is no formal definition of "extended ASCII", and even use of the term is sometimes critic ...

" 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 "."Configuring Netscape Mail On Unix: Why the Content-Length Format is Bad"
by Jamie Zawinski 1997 Until

8BITMIME The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typi ...

, a variety of

binary-to-text encoding A binary-to-text encoding is encoding of data in plain text. More precisely, it is an encoding of binary data in a sequence of printable characters. These encodings are necessary for transmission of data when the channel does not allow binary ...

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.

References

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References

See also