Actually seems interesting...Electronic Circuits... I never got to actually learn these types of circuits...but I'm interested in knowing....What can it be used for?Sorry, I had misspelled; its tow-thomas-biquadraitc filter; anyways, its a BiQuad filter...but by using Op-Amps, resistors and caps you can create a stable bandpass filter (butterworth); Convolution was thrown in because you can use a convulved signal with such a filter. They really are fun to build, not so much finding the transfer functions.
Edit: BiQuad: You should have quadratics in the denominators with in the "S" domain--when finding the appropriate transfer functions