Provided is a phantom for evaluating the accuracy of image registration software based on a result of matching tomograms of a predetermined position of the phantom, taken using two or more imaging apparatuses. A switch transistor is operatively coupled between the output of the power transistor and the control transistor to selectively activate the control transistor in response to an over current condition detected by a defect transistor. Thereafter, a latency is determined with which the entering peer is to receive the data content with respect to a real-time playback point of the data content distributed by the streaming source.