The HT903 accessory was designed for connection with multipurpose meters like GSC5x, HT9032, HT202E on three-phase systems through external fixed CTs for high current measurements over 3000 Amps. The HT903 is housed in a wooden box, it receives signals from the CTs secondary with 1A or 5A ratio on its input terminals and transforms it, with linear relationship, in a 1V AC output signal to an analyzer inputs. The HT903 is supplied with a set of cables for connection to CTs and meters/analyzers according to EN61010-1 standard on CAT II 300V.