magnetic field generated by the EnSite Precision Field Frame
http://kivra.kpi.ua/wp-content/uploads/file/rtpsas_2016/RTPS...
Эмиттер магнитного
поля помещается под операционный стол и состоит из трех катушек
(Рис. 1), которые генерируют низкие поля, кодируя картируемое пространство вокруг грудной клетки пациента.

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Note added at 22 hrs (2018-08-17 14:14:53 GMT)
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https://europepmc.org/articles/pmc6009785
Ensite Precision
The EnSite Precision Cardiac Mapping System, which is available since 2016, also uses the advantages of hybrid impedance and magnetic field technology for localization of the catheters insight the body. It allows a much higher precision and more accuracy over the entire investigation time compared to the predecessors EnSite NavX and Ensite Velocity. The system consists of the following components: the EnSite Amplifier (which converts the physiological signals from the patients to digital signals for processing by the workstation), the EnSite Precision Field Frame, the display workstation and eight surface electrodes (three transthoracic pairs for three orthogonal axes and two patient reference sensors). It is, compared to the CARTO system, an open platform with compatibility to almost any electrophysiology catheter for mapping cardiac chambers. The basis for impedance-based localization and tracking of the catheters is the proven EnSite NavX Navigation and Visualization technology of previous EnSite systems. The new hardware equipment allows the additional use of the new Sensor EnabledTM (SE) technology. The therefore necessary EnSite Precision field frame is (like the location pad of the CARTO system) attached under the catheter table and generates a weak magnetic field.