• Communications
  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...
  
   equipment at either end of a communications link
  Data link
  In telecommunication a data link is the means of connecting one location to another for the purpose of transmitting and receiving information. It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver and the interconnecting data telecommunication circuit...
  
  , used to permit the stations involved to accomplish the mission for which the link was established.
• In radio
  Radio
  Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
  
  -relay
  Relay
  A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...
  
   systems, equipment used at points where data
  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...
  
   are inserted or derived, as distinct from equipment used only to relay a reconstituted signal.
• Telephone
  Telephone
  The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
  
   and telegraph switchboards and other centrally located equipment at which communications circuits are terminated.

See also

• Customer-premises equipment
  Customer-premises equipment
  Customer-premises equipment or customer-provided equipment is any terminal and associated equipment located at a subscriber's premises and connected with a carrier's telecommunication channel at the demarcation point...
  
  
• Data terminal equipment
  Data terminal equipment
  Data Terminal Equipment is an end instrument that converts user information into signals or reconverts received signals. These can also be called tail circuits. A DTE device communicates with the data circuit-terminating equipment...
  
  , an end instrument that converts user information into signals for transmission or reconverts the received signals into user information