Housing for inmates may be either single cell units or dormitories when the areas are secure and designated for this purpose. It shall also include a secure perimeter, occupied 24 hours a day, together with some form of external patrol and detection devices.

The correct answer is focused on medium security housing for inmates, which typically includes configurations such as both single cell units and dormitories. In a medium security facility, the areas are designed to securely house inmates while allowing for some level of interaction among them, which is characteristic of dormitory settings. Such facilities are equipped with secured perimeters, meaning they have barriers and fencing to prevent escapes or unauthorized access.

A secure perimeter that is staffed or monitored 24 hours a day is essential for maintaining the safety of both the inmates and the staff. This often includes external patrols and detection devices to enhance security and ensure the proper management of the facility. The conditions signify that while the inmates in this environment may have more freedoms compared to a maximum security setting, there are still substantial measures in place to prevent any potential risks.

Minimum security is typically less restrictive and may not include secure perimeters in the same way. Disciplinary security often pertains to inmates in a separate context, likely involving those who have violated rules within a facility, leading to more punitive measures rather than general housing classification. Maximum security is more restrictive than medium security, with higher levels of control and limited inmate movement, making it unsuitable for the description provided in the question.