This page has links to documents about the modem behavior and TNC protocols created by Nino KK4HEJ for the TARPN NinoTNC.
As of this writing, June 2022, the NinoTNC supports 6 bit-rates, 150, 300, 1200, 2400, 4800 and 9600.
The 150 baud is AFSK 1600 and 1800hz tones
The 300 baud is AFSK 1600 and 1800hz tones
The 1200 baud mode is Bell 202.
The 2400 baud mode is a new digital audio phase shift keying mode described in the PDF linked below.
The 4800 baud mode is a modification of the G3RUH mode where the bits are sent for twice as long.
The 9600 baud mode is G3RUH.
The NinoTNC supports AX.25 and also Improved layer 2 Protocol.
IL2P is described in the PDF linked below.