Telephone Jack

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What Does Telephone Jack Mean?

A telephone jack is a socket into which a connector that is used to connect a telephone to a building’s wiring is plugged. It acts as a hardware interface between the telephone wiring and the telephone, and is considered the counterpart of the telephone plug. It is usually fixed to the wall or baseboard.


Every country follows a particular standard for the design and use of telephone jacks. The most commonly used telephone jack standard is the RJ-11 modular connector. The telephone jack forms a part of the dial-up systems used by home computers to connect to the Internet.

Al telephone jack is also known simply as a phone jack.

Techopedia Explains Telephone Jack

The telephone jack is used to connect the telephone to an external telephone wiring. It consists of conductor wires through which data can be transmitted both to and from an external telephone cable and a telephone.

The following are the most common types of telephone jacks:

  • Flush plate — A wall-mount jack that sticks out from the wall, allowing the telephone to be mounted on the wall
  • Wall mount — A wall-mount jack that allows for plugging in the phone but does not mount it
  • Baseball jack — A type of jack that consists of small plastic or metal boxes fixed to a baseboard. The jack opens at the bottom edge of the box.

There are many more variations of telephone jacks, including a duplex jack that allows connecting to two separate lines. This type of jack can be used to connect to both a DSL Internet connection and a phone line. Wireless phone jacks are also available and are used along with modems to connect telephones without a phone jack cable or line.

The jack used in each country can differ, as there are many jack standards. The most commonly used jack standard is the RJ-11, which is considered to be an international standard. As different standards are used, sometimes phone jacks may require an adapter and a phone cord to connect a phone.

The following are some of the most common telephone jack standards:

  • RJ-11 — This jack has six conductors and is usually implemented with four conductors. The four wires used are grouped as a red-and-green and a black-and-white colored pairs. Dial-up modems are connected to a network using RJ-11 jacks.
  • RJ-14 — This jack also has four wires, which are used for two phone lines.
  • RJ-45 — This is a single-line jack used in digital data transmission, with a data rate of up to 19.3 Kbps.

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.