A system includes plural sensors to detect at least one of a magnetic field and an electrical field, where each of the plural sensors includes outputs that output sensor signals when a field is detected. Plural signal modulators receive sense signals that correspond to sensor signals from corresponding ones of the plural sensors. Each of the plural signal modulators has first and second control states. In the first control state, each signal modulator outputs sense signals, and, in the second control state, each signal modulator outputs inverted sense signals. A device receives and processes the sense signals or the inverted sense signals.