Editing Terminal node controller (section)

== Description ==
{{Unreferenced section|date=September 2016}}
[[File:Terminal-Node-Controller-Kantronics-9612plus-0a.jpg|thumb|The Kantronics 9612+ was implemented around an [[8-bit]] [[Motorola]] [[microcontroller]].]]

A typical model consists of a [[microprocessor]], a [[modem]], and [[software]] (in [[EPROM]]) that implements the AX.25 protocol and provides a [[command line interface]] to the user.  (Commonly, this software provides other functionality as well, such as a basic [[bulletin board system]] to receive messages while the operator is away.)  Because the TNC contains all the intelligence needed to communicate over an AX.25 network, no external [[computer]] is required.  All of the network's resources can be accessed using a [[dumb terminal]].

The TNC connects to the terminal and a radio [[transceiver]].  Data from the terminal is formatted into AX.25 packets and [[modulation|modulated]] into audio signals (in traditional applications) for transmission by the radio.  Received signals are demodulated, the data unformatted, and the output sent to the terminal for display.  In addition to these functions, the TNC manages the radio channel according to guidelines in the AX.25 specification.

Early usage was mostly one-to-one communication, either between two people or a person to an automated Bulletin Board or E-mail system.