TRANSTECTOR's HT-NO-E3PM-GPST. HEMP tested (TM) to MIL-STD-188-125, the E3PM HT GPS surge protector is designed to provide electromagnetic pulse (EMP) protection for equipment and facilities per Department of Homeland Security (DHS). Using silicon technology, the E3PM HT GPS provides an integral electromagnetic interference (EMI) filtering and EM clean or dirty barrier.