A defensive shield, commonly referred to as simply a shield and sometimes as a Holtzman shield, was a protective energy field that could surround the person who wore it.
A shield was produced by a Holtzman generator, the field deriving from Phase One of the suspensor-nullification effect. Shields can be calibrated to permit the passage of matter below given speeds. This is vital in personal defense shields, as one would suffocate within a shield that did not admit atmospheric gasses. Depending on the shield’s setting, the object’s speed while passing through the shield would range from six to nine centimeters per second. A shield could also be set to cover either the left or right side of a person if the specific need for it arose.
Shields used to protect installations can and usually do have far lower penetration velocities, as life support technologies can be used to recycle atmosphere while the shield is active.
However, if a lasgun beam hit a Holtzman field, it would result in sub-atomic fusion and a nuclear explosion. The center of this blast was determined by random chance; sometimes it would originate within the shield, sometimes within the laser weapon, sometimes both.