Information-gathering apparatus which has functions to store the data measured by remote monitoring and to send a stored data upon request, namely, electronic recorders for storing and archiving information related to temperature, pressure, flow and other physical data from sensors; data acquisition apparatus which has functions to store the data measured by remote monitoring and to send a stored data upon request, namely, mobile data receivers and mobile data receivers using communication networks; data loggers, namely, electronic measuring devices, namely, temperature indicators, temperature sensors, pressure gauges, pressure indicators, flow meters; data collecting devices, namely, apparatus for recording data in the nature of temperature, pressure, flow and other such physical data from sensors; record and display units of measurement data, namely, video monitors for recorded wave forms of measured data and measured values; computer programs for analyzing measured data; measuring apparatus, namely, signal analyzers for analysis of abnormal conditions of signals of measured data related to temperature, pressure, flow and other physical data from sensors; electric and magnetic meters and voltage testers