According to one embodiment, a server 11 performs aggregate signal processing for n-to-one signal transmission. The processing includes waiting processing and time adjusting processing. In the waiting processing, from a time point where a first constitutional element signal constituting a specific aggregate signal bound for the upper level control center reaches the server until a wait time that is based on a preset condition elapses, the server waits for another constitutional element signal of the specific aggregate signal to arrive (S202-S208). In the time adjusting processing, the server extracts an earliest generation time from generation times attached respectively to constitutional element signals arriving during the waiting processing, and attaches the extracted time as a generation time of the specific aggregate signal (S210).