SMALL FUSE - BIG PROTECTION FOR GENERAL CIRCUITS Amp-trap ATMR fuses, in the Class CC family, are the smallest dimension 600V fuses suitable for branch circuit protection. The ATMR is a popular choice for economical protection of control circuits and control circuit transformers where available short circuit currents exceed 10,000 amperes. ATMR's rejection dimensions prevent substitution by lesser rated fuses. These fast acting fuses give current limiting protection to general circuits.