The secondary supply voltages are electroni-cally protected against overload or short cir-cuit. The primary line voltage side is protected by a fuse located on the power supply unit. The fuse rating covers the full voltage range. Con-sequently there is no need for the user to re-place the fuse under any operating conditions, nor is it accessible from the outside.

CAUTION: If this fuse is blown, it is likely that the power supply is badly damaged. do not replace the fuse. Send the frequency standard to the local Pendulum Service Cen-ter.