Abstract: A two-part electrical surge arrester for protecting electrical equipment within a shielded enclosure from electromagnetic pulses and lighting on incoming lines. One part mounted on the exterior of the enclosure wall includes a chamber having fifty-five spark gaps employing a common ground plane. The second part mounted on the interior of the enclosure wall contains fifty-five current limiting resistors and fifty-five low pass filters. When both parts are mounted on opposite sides of the enclosure wall contacts from each engage through an opening in the wall to provide fifty-five protective paths between incoming lines and equipment within the enclosure.