A terminal node controller (TNC) is a device used by amateur radio operators to participate in AX.25 packet radio networks. It is similar in function to the Packet Assembler/Disassemblers used on X.25 networks, with the addition of a modem to convert baseband digital signals to audio tones.
AEA (Advanced Electronic Applications Inc.) PK-232MBX, circa 1991
The Kantronics 9612+ was implemented around an 8-bit Motorola microcontroller.
In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital data via a radio communication link.
Terminal Node Controller 2400 baud packet radio modem