NETA Certified Technicians (Level III and Level IV) are required to earn a minimum of 48 CTDs every three years to maintain their certification. For more information about the CTD program and requirements, please contact the NETA office at neta@netaworld. All Doble protection training courses are presented in an easy to understand format with real life case studies and examples for a truly unique training experience. They have achieved NETA Certification at Level 2, Level 3 or Level 4 through successful completion of the NETA examinations and meet continuing education, training, and years of experience requirements.