IBM's in-car digital video system continuously records images and sound onto a 40- or 60-GB hard drive. When the officer turns on his overhead pursuit lights, the previous four minutes of video and audio are saved and recording continues until the officer turns off the system. The system uses Coban Technologies; Video Mobile Data Terminal to collect data via digital video cameras mounted in cars and audio captured on microphones worn by officers. The data is fed to a ruggedized computer hard drive in the vehicle. At the end of the shift, the patrol officer brings the hard drive into police headquarters and uploads recorded images into a central data repository. IBM also can equip the system with wireless capability to permit near real-time transmission of video images and sound. Unique authentication keys discourage video file tamperating. Images can be synchronized with other relevant information such as speed radar readings, GPS data, vehicle telemetry and lightbar activity.