SMAR's SD1 Magnetic Tool is the second human-machine interface used to perform local adjustments in transmitters and converters manufactured by Smar. This tool adds the advantages of the powerful HHT to the practicality of the "good and old" screwdriver. The instruments have, under the nameplate, holes for two magnetic keys activated by the magnetic key. If the transmitter or converter is equipped with a display, and configured for Full Local Adjustment, the magnetic key is almost as powerful a resource as the HHT. In this case, the magnet key eliminates the need for HHT in most basic applications.