Prison

A prison, correctional facility, detention center, jail, gaol, penitentiary or remand centre is a facility in which inmates are forcibly confined and denied a variety of freedoms under the authority of the state. Prisons are most commonly used within a criminal justice system: people charged with crimes may be imprisoned until they are brought to trial; those pleading or being found guilty of criminals at trial may be sentenced to a specific period of imprisonment. Beside their use for punishing crimes, jails and prisons are frequently used by authoritarian regimes against perceived opponnents.

Security
Prisons are normally surrounded by walls, fencing, earthworks, geographical features or other barriers to prevent escape. Multiple barriers, electrified fencing, concertina wire, secured and defensible main gates, armed guard towers, security lighting, motion sensors, dogs and roving patrols may also be present depending on the level of security. Remotely controlled doors, CCTV monitoring, alarms, cages, restraints, non-lethal and lethal weapons, riot control gear and physical segregation of units and prisoners may also be present within a prison to monitor and control the movement and activity of prisoners within the facility.

Modern prison designs have increasingly sought to restrict and control the movement of prisoners throughout the facility and also to allow a smaller prison staff to monitor prisoners directly; often using a decentralized podular layout. Smaller, separate and self-contained housing units known as pods or modules are designed to hold 16 to 50 prisoners and are arranged around exercise yards or support facilities in a decentralized campus pattern. A small number of prison officers, sometimes a single officer, supervise each pod. The pods contain tiers of cells arranged around a central control station or desk from which a single officer can monitor all the cells and the entire pod, control cell doors and communicate with the rest of the prison.