Mark and space are terms used in

telecommunications 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 fe ...

to describe two different signal states of a communications signal, generally at the physical layer of a communications system. The terms derive from the early days of the

electric telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...

system, where the ''marking'' state would cause a mark to be output on paper, and the ''spacing'' state would create no mark. The terms would continue to be used in systems such as

RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such ...

, with similar conventions, that "mark" would be encoded by a negative voltage (or current flow), and "space" by a positive voltage (or no current flow). In such systems, the line is typically left in the "mark" state when idle. "Mark" is generally identified with the

binary digit Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two digits (0 and 1) * Binary function, a function that takes two arguments * Binary operation, a mathematical operation that ta ...

"1" and "space" with the binary digit "0".

References

See also