Which of the following is a device used for visitor security checks?

The metal detector is a widely recognized device utilized in various security settings, including visitor security checks in correctional facilities. These detectors are essential for ensuring that individuals entering the facility do not carry prohibited items or weapons. The metal detector works by emitting an electromagnetic field and detecting metallic objects that disrupt this field, thus alerting security personnel to potential threats.

In the context of visitor security checks, the metal detector is effective in screening for items such as guns, knives, and other contraband that could endanger staff, inmates, or visitors themselves. Its use is practical and efficient, allowing for a quick and thorough examination of visitors as they enter the facility.

While under-car cameras and biometric scanners also contribute to security in different ways, they do not specifically serve the purpose of screening visitors directly for forbidden items. Under-car cameras are primarily utilized for surveillance of vehicles to check for contraband hidden underneath, while biometric scanners focus on identifying individuals through unique physical traits, such as fingerprints or iris patterns. Facial recognition software can enhance security by identifying individuals based on their facial features, but it does not actively detect physical objects like a metal detector does. Thus, the metal detector stands out as the most appropriate device for conducting visitor security checks in correctional environments.