A ring modulator has 2 inputs and 1 output. The output mixes 2 signals: the sum and the difference of the 2 input signals. If the input signals are 600Hz and 200Hz sine waves, the output is a mix of a 400Hz sine wave (600Hz - 200Hz) and a 800Hz sine wave (600Hz + 200Hz). With other wave forms you also have harmonic frequencies which makes the output signal much more complex.
Submitted on October 13, 2004