Defense screens were a defensive technology used by Peacekeepers. When activated, they surrounded ships with a red energy field in an oval-shaped bubble which was capable of protecting anything inside of it from kinetic or energy attacks. Defense screens could also protect vessels from gravitational pulls.
Defense screens are, however, highly imperfect. They take time to power up to full capacity, and at less than full capacity damage may be taken -- or other strange side effects may occur. While Moya's defense screen was at 62%, a Halosian attack caused the crew members to switch bodies. For this reason, vessels that had the energy capacity to keep their defense screens activated all of the time typically did so. Defense screens also contained a number of holes in the energy field, which left ships inside vulnerable. Most of these holes could be filled by having two defense screens active.
Though command carriers were always equipped with two defense screens, always activated. Few other vessels had the capabilities of doing so. The crew of Moya took a defense screen from the wreckage of the Zelbinion but the energy reserves of a Leviathan biomechanoid did not permit them to keep the defense screen active at all times.
Defense screens remained in use by the Peacekeepers for many cycles, although the technology was much improved by the time the United Federation of Planets made contact. At this point, the Peacekeepers engaged in technological trades with the Federation and began to develop similar shield technologies. Defense screens fell out of use.
Defense screens are seen in Farscape.