The intrinsic safety of the NetModule Routers is implemented as follows:
NB37xx: Both power inputs are secured by non resettable fuses (Fuse Schurter OMF125, 5A, quick acting)
NB27xx, NB1600: The plus pole of the power supply is protected against internal short circuit by a PTC (Multi-fuse, Ihold=1.1A, Itrip=2.2A @ 23°C, 72V)