This adapts our MiniDIN-6 TNC cable to take the signal from pin 4 (1200 baud, de-emphasized audio) instead of pin 5 (9600 baud, discriminator output). For most radios, our TNC works best using the discriminator output. However, some radios provided a very low signal on this pin or, like the FT-991, no signal at all from pin 5 of the data port.
This adapter is only really useful with the Mobilinkd MiniDIN-6 cable. It routes pins 1, 2, 3 and 6 straight through, and routes pin 4 to pin 5.