Lion´s twin-T circuit revisited

A circuit patented by Kurt S. Lion in the 1950s, which essentially acts as a transducer, converting the changes of a variable capacitor into a DC voltage, is discussed. This circuit, which appears to have been forgotten, has definite advantages, especially as an efficient processing network for capacitive transducers. The authors offer a full qualitative and quantitative description (equations are cleanly treated with the Laplace transform), and describe the experimental results obtained in their laboratory. Design criteria are presented, and some possible applications in biomedical engineering are suggested.<>