A friction body of porous carbon, which is infiltrated with silicon and reinforced with carbon fibers, includes at least one separate friction layer on a core body. In one embodiment, a monolithic inductance-enhancing integrated circuit comprises a transistor supported by a bulk monocrystalline silicon substrate. A gate of one of the differential pair can receive the control signal and a gate of the other of the differential pair can receive a logical inverse of the control signal. For example, the transducer comprises electronic circuitry configured to encode the digital data in a signal for transmission to the sensor.