What is the difference between DO and AF signal?

AF is an abbreviation for Audio Frequency and the same as the sound signal output from FM radios. Since the data rate of our radio modules is equal to or under 9,600bps, the de-modulated signal is within the audio spectrum and it is audible (i.e 9,600bps equates to 4800 kHz). AF signal is approx 100mV. In order to interface with digital systems, AF signal will be converted to two levels (Low = 0V and High = Vcc) using a data slicer circuit and then output from the DO.