An operator of a radio paging system for private use. PPOs are unregulated, but must share unlicensed spectrum with other users in the VHF and UHF bands. Enterprises operating in large campus environments may operate private paging systems. Restaurants often operate private paging systems to notify servers when orders are ready or to notify diners when a table is available. See also paging system, radio, spectrum, UHF, and VHF.