AFSK 1200 X.25 APRS Modulator & Demodulator
Detect AFSK 1200 X.25 APRS Packet from SoundCard and Console Out it
(see window.png) 
You can use it as c# library for exchanging digital packet data between hamateur radios via air.
Just use AFSK1200Modulator as DAC and AFSK1200Demodulator or DirectAudioAFSKDemodulator as ADC.
Full samples available at AFSK1200ModemTest.cs or in based-on APRSAIR application