There are two other read modes, FSK and PSK, which must be mentioned as well. FSK (frequency shift keying) modulation is very similar to ASK modulation, the only difference appears in the bit length for the logical 1 and 0. The diagram on this slide shows, for example, ten cycles (five low and five high) for a logical 1, and eight cycles (four and four) for a logical 0. PSK (phase shift keying) modulation is also very similar to ASK modulation, but as can be seen in the diagram the modulation changes with every clock cycle. While one cycle is being modulated, the following one remains umodulated, and so on. In case of bit value changes, the modulation scheme is different, there are always two consecutive modulated or respectively un-modulated cycles.