Positive Train Control or PTC is a new GPS and data system to enforce various railroad and federal rules pertaining to train movement. Most railroads will be required to use a form of PTC currently offered by two vendors. This system is designed to be interoperable with other railroads to allow standardizing of data and equipment. Some isolated or passenger railroads may use their own form of PTC such as Amtrak's ACSES on the Northeast Corridor. PTC is independent of other forms of signaling such as ATC/CCS/ATC, but may be overlaid with signal systems. Although there is no dedicated service for PTC by the FCC, railroads have selected the 220MHz spectrum for PTC operations. These frequencies are licensed nationwide.