Security services are primarily a system for the control of the campus, to maintain a secure environment. On all campuses, over 1000 cameras have been installed, along with dozens of infrared sensors, to monitor the entrances and exits to every building, as well as corners of the stairwells. All cameras are monitored in either the central control center or campus security room. Recording continuously, 24 hours a day, the input is saved digitally, with requested images available for checking through the intranet. Each image is processed through a switch to a digital video recorder and a 16-bit video compressor. The digital video recorder transmits the images to the central control room center, allowing the central control room to use a control keyboard to inspect necessary images. Following an incident, images from a specified time can be inspected, and if necessary be converted to video tape or digitalized to serve as evidence for an investigation.