Guildline’s 6645Q Quantum Hall System has been designed and developed to meet the needs of Standards Laboratories around the world for an improved level of accuracy in the calibration and maintenance of primary resistance standards. The 6645Q System is based on over 60 years of Guildline expertise in precise resistance measurements and on over 50 years of design and manufacturing expertise with Direct Current Comparator (DCC) Resistance Bridges. Guildline has being working closely with Oxford Instruments, a company that also has over 50 years of experience, to supply the cryogenic and superconducting magnet systems; and with a leading National Metrology Institute (NMI) that has over 20 years of experience developing semiconductor Quantum Hall Effect (QHE) sensors. Guildline has fully integrated all required system components to provide customers with an advanced, easy-to-use, fully automatic QHR System.