A system for processing signals received from an apparatus, said system comprising: an apparatus, the apparatus comprising: an expandable structure (22, 76), configured for insertion into a body of a subject; and a plurality of conducting elements (24, 74) coupled to the expandable structure, each of the conducting elements comprising a respective coil (24, 80), the coil comprising: an insulated portion that is electrically insulated from tissue of the subject, and an uninsulated portion configured to exchange signals with the tissue, while in contact with the tissue, to acquire intracardiac ECG signals; wherein the coil is configured to output signals in the form of induced voltages in response to a magnetic field; circuitry configured to generate, based on the intracardiac ECG signals received from the conducting elements, a plurality of first outputs and, based upon the induced voltage signals received from the conducting elements, a plurality of second outputs, wherein each second output indicates the position of the respective conducting element; and a processor, configured to use the plurality of outputs to construct an electroanatomical map, wherein the processor is configured to derive, for each conducting element, electrical-activity information from the first output and the position of the conducting element from the second output, and to combine the electrical-activity information with the position of the conducting element to construct the electroanatomical map. an apparatus, the apparatus comprising: an expandable structure (22, 76), configured for insertion into a body of a subject; and a plurality of conducting elements (24, 74) coupled to the expandable structure, each of the conducting elements comprising a respective coil (24, 80), the coil comprising: an insulated portion that is electrically insulated from tissue of the subject, and an uninsulated portion configured to exchange signals with the tissue, while in contact with the tissue, to acquire intracardiac ECG signals; wherein the coil is configured to output signals in the form of induced voltages in response to a magnetic field; an expandable structure (22, 76), configured for insertion into a body of a subject; and a plurality of conducting elements (24, 74) coupled to the expandable structure, each of the conducting elements comprising a respective coil (24, 80), the coil comprising: an insulated portion that is electrically insulated from tissue of the subject, and an uninsulated portion configured to exchange signals with the tissue, while in contact with the tissue, to acquire intracardiac ECG signals; wherein the coil is configured to output signals in the form of induced voltages in response to a magnetic field; an insulated portion that is electrically insulated from tissue of the subject, and an uninsulated portion configured to exchange signals with the tissue, while in contact with the tissue, to acquire intracardiac ECG signals; wherein the coil is configured to output signals in the form of induced voltages in response to a magnetic field; circuitry configured to generate, based on the intracardiac ECG signals received from the conducting elements, a plurality of first outputs and, based upon the induced voltage signals received from the conducting elements, a plurality of second outputs, wherein each second output indicates the position of the respective conducting element; and a processor, configured to use the plurality of outputs to construct an electroanatomical map, wherein the processor is configured to derive, for each conducting element, electrical-activity information from the first output and the position of the conducting element from the second output, and to combine the electrical-activity information with the position of the conducting element to construct the electroanatomical map.