Equipment and systems for protecting electronics against damage or upsets from electromagnetic pulse (HEMP or EMP), intentional electromagnetic interference (IEMI), and high power RF weapons are disclosed. This equipment can include a shielding arrangement includes a metallic enclosure having an interior volume defining a protected portion and an unprotected portion separated by an electromagnetically shielding barrier, and having a portal providing access to the protective portion and including an access opening, a shielding cover sized to cover the access opening, and an electromagnetically sealing gasket positioned around a perimeter of the access opening. The shielding arrangement also includes one or more filters positioned at least partially within the unprotected portion and along the electromagnetically shielding barrier to dampen electromagnetic signals and/or power signals outside a predetermined acceptable range. In some cases, waveguides beyond cutoff are included, to provide passage of optical signals or airflow through the enclosure.