solutions that only needed a radio and an optional dumb terminal. As home computers made their way into ham "shacks," there was a movement toward simpler, cheaper "KISS" (Keep It Simple, Stupid) devices. These have a modem and minimal processing of the AX.25 protocol. Most of the processing is moved to the personal computer. The next logical step in the evolution is to eliminate the specialized hardware and move all of the processing to a computer. A "soundcard" is used for audio to and from the radio. Everything else is done in software. Some of the earlier attempts performed poorly, giving this approach a bad reputation. Modern software TNCs, using digital signal processing (DSP) techniques, can successfully decode poor quality signals that the older equipment can't. Some handheld and mobile VHF radios currently on the market incorporate TNC abilities within the radio itself in support of the APRS protocol. Many TNCs are still in use, especially in unattended stations where reliability is important. The importance of location to the APRS system has fueled development of a new generation of small low-power TNCs often integrated with a GPS module for use in mobile tracking stations. APRS digipeating protocols require specific naming conventions, and older TNCs may not have the required support to be used as a digipeater. However, almost any TNC can be pressed into service for Home or Tracker use. TNCs that were clones of the popular TAPR TNC-2 may be upgradeable via the UIDIGI firmware project. TNC/Radio data ports Although typically described as data ports, the interface between a radio and a TNC is almost entirely analog audio (plus lines for PTT and squelch). The connectors used for this purpose vary widely across TNC manufacturers, but modern radios that offer data ports have widely adopted the Mini-DIN 6-pin connector. Also used are full-size DIN connectors, modular telephone (RJ) connectors, and combinations of mini- and micro-headphone connectors (typically on handheld radios). 6-pin Mini-DIN Terminal data port TNCs were originally designed to accept messages from a human typing on a dumb terminal. TNCs had a DB-25 or DE-9 connector carrying asynchronous start-stop bytes with RS-232 signal levels. This could also be used with the serial port of a personal computer. Serial ports are now pretty much extinct, but USB-to-serial converter cables are available. However, typically a human uses a more sophisticated software package running on a personal computer that sends messages