Hydraulic fuses fitted to all the brake lines at the A/Skid modules they are there to protect the integrity of the hydraulic systems if a brake line is damaged. They are a simple poppet and spring with a manual reset lever and 'trip' if there is a sudden high flow rate and drop in pressure downstream.
The other hydraulic fuses are there to protect the hydraulic system integrity if the rear pressure bulkhead should fail (JAL 123) these are basically the same except they are self resetting when the pressure either side of the poppet is equal. (+/- 5psi)