An integrated circuit comprising a plurality of portions, each portion including test control circuitry; and at least one test input arranged to receive test signals, the circuit having a test mode in which one or more of the plurality of portions are testable, wherein the circuit has a reset mode which has priority over the test mode. When tethered by the nose of the housing, the water current rotates the turbine blades generating electrical current which is supplied for commercial use via the tether to a land-based utility. The calibration mechanism mitigates the need for frequent error correction and does not incur the performance degradation associated with error correction techniques.