Phoning home could also be for marketing purposes, such as the "Sony BMG Rootkit", which transmits a hash of the currently playing CD back to Sony, or a digital video recorder (DVR) reporting on viewing habits. High-end computing systems such as mainframes have had 'phone home' capabilities for many years, to alert the manufacturer of hardware problems with the mainframes or disk storage subsystems (this enables repair or maintenance to be performed quickly and even proactively under the maintenance contract). Similarly, high-volume copy machines have long been equipped with phone-home capabilities, both for billing and for preventive/predictive maintenance purposes.