 Previous systems using phase shift keying (PSK) encoded two bits (or sometimes three) per symbol by slightly delaying or advancing the signal's phase relative to a set carrier tone.QAM used a combination of phase shift and amplitude to encode four bits per symbol.Transmitting at 1,200 baud produced the 4,800 bit/s V.27ter standard, the same working at a base rate of 2,400 baud produced the 9,600 bit/s V.32.