Conspec's P1547 Portal Protector board is designed to prevent stray surges or transient voltages from entering the trunk cable. This card will prevent surges from traveling the cable and destroying electronic components, which operate from low DC voltages. The unit is installed as a junction box on the line, and grounded before entering the mine portal.

The portal protector board contains fuse discharge chambers and buss fuses for circuit connections. A quantity of (4) fuses rated five amps is supplied, but lower rated fuses may be substituted depending on the requirements.