Video signal processing devices are used to separate or group together the images received from multiple video cameras. Cselectors can be utilized to display the images from multiple video cameras in sequence in full screen mode. The numerous accessories make it possible to complete the system even when special functions are required: they include hard disks to increase the storage capacity of the DVR, transmission systems other than those using standard video cable, signal distributors, amplifiers and special equipment for calibration of the optics and phase control.