It is a aM fuse-link that protects against magnetic over currents only, adapted for motor protection. Its current rating is 4 A and the maximum rated voltage is 690 VAC. They are ideal for protecting sensitive electronic components that require rapid response to overcurrent conditions. F = Fast. Ceramic Fuses Cartridge Fuses are available at Mouser Electronics. Specifies dimensions and performance requirements for general purpose cartridge fuse links of current ratings not exceeding 13 A for domestic and similar purposes on declared supply voltages not exceeding 250 V at a nominal frequency of 50 Hz.