The 7151-10, -20, -40, and -50 are clock generators for EMI (Electro Magnetic Interference) reduction (see below for frequency ranges and multiplier ratios). Spectral peaks can be attenuated by slightly modulating the oscillation frequency. Both down and center spread profiles are selectable. Down spread maintains an average frequency less than an unspread clock, and will not exceed the maximum frequency of an unspread clock.