Who has the authority to service or modify GMDSS radio equipment?

According to the GMDSS regulations, GMDSS ships that opt for at-sea maintenance must have a certified GMDSS radio maintainer on board. Individuals with a GMDSS Radio Maintainer’s License, a Radiotelegraph Operator License, a First or Second Class Radiotelegraph Operator’s Certificate (T, T-1, or T-2), or a General Radiotelephone Operator License are required to maintain the equipment.