Circuits, systems and methods that utilize two transducers, of which at least one is a piezoelectric transducer, adapted and coupled to receive and/or generate signals in the forms of sound waves, mechanical vibrations, and/or electromagnetic energy. In one version, two transducers each receive and/or generate separate vibrational energy signals that bear information. Two or more transducers coupled to a switching circuit may send or receive piezo-electrical circuit output signals that include a carrier wave having different frequencies that are within separate frequency ranges. Two or more transducers may generate output signals that are simultaneously processed by or multiplexed by a switching circuit.