Related to a synchronization method using a device not connected to a network, Sugimoto, et al. dvocated Display based Computing [8] which is a concept to achieve communication, measurement, control and appropriate presentation that exert influence on the real world by using display devices. Since it supposed to utilize the existing infrastructure, this concept has cost-benefits. In broadcasting
service required to be public service, this point has considerable merits. Hence, we adopted the concept to achieve an accurate synchronization not with a network but using just display.