A circuit for a high speed digital multiplexer has an active load circuit connected to an output of the digital multiplexer. The method involves creating a computer simulation model of a ship, optimized for fuel efficiency. In a first example embodiment, a first piezoelectric assembly comprises a first or main piezoelectric diaphragm connected to the actuator element for displacing the actuator element in response to displacement of the first piezoelectric diaphragm. This topology together with the use of low frequencies permits area reads, and permits small and economical passive tags, and further permits localization of a particular passive tag as being nearby to a particular active tag.