In correctional institutions, portals are often at access/egress points where staff, inmates, and visitors must pass through for detection of contraband (e.g., cell phones, weapons, drugs, money, escape plans, and explosives) hidden on the body or, in some cases, within the body. The National Institute of justice's (NIJ's) Institutional corrections Technology Working Group (TWG) believes contraband detection is such an important issue that it has recommended as a high priority the development of a portal device that will integrate and improve existing methods of detecting a broad spectrum of contraband, such as (but not limited to) metallic and nonmetallic weapons, drugs, tobacco, and wireless communication devices. Descriptions of the features and functions of portal types covers metal detectors; millimeter wave detection devices, which can detect foreign objects concealed on a person's body under layers of clothing; magnetometer (gradiometer) metal detection; electric field tomography, which projects weak electrical energy into a person's body and is being considered for the imaging of contraband hidden inside a body; ion scan technology, which senses organic compounds such as drugs and explosives; and heartbeat detection, which listens to vehicles parked in perimeter sally port enclosures for indications of a human heartbeat. Also currently available is backscatter x-ray contraband detection, which can be used at personnel security checkpoints and as a device that searches for contraband in vehicles in sally ports. The report concludes with a listing of security operations that should complement the use of portal contraband detection technology. Sources for more information