Terminal Node Controller – a modem for packet radio operations.
A TNC sits between a computer and radio transceiver, and converts digital data from the computer to FSK or AFSK signals that can be transmitted by the radio. It also converts signals received by the radio to digital data for use by the computer. TNCs are commonly used for Winlink and APRS on VHF and UHF bands. Typical data transfer rates are 1200 and 9600 bits per second.