1. An inventory control system for a digital signage network having a plurality of screen zones associated with a plurality of displays connected to the network, each screen zone displaying at least one item of media content for a predetermined period of time, the system comprising: a database that maintains a record of the display schedule of each of the screen zones, the schedule covering, for each screen zone, said predetermined period of time during which media content items assigned to the schedule are displayed; and a scheduler that receives a scheduling request, assigns media content items to specific screen zones to be displayed during said predetermined time periods and updates the record of the display schedule to reflect corresponding changes therein.