Abstract: A scanning circuit successively scans a multiplicity of input points, producing respective binary signals representing corresponding status in a chemical or electrical industry. The scanned output is stored in an update memory at an address which corresponds to each of the input points. Each of the scanned output is also compared with a signal read out from this memory which stores the result of the previous scanning, and in the absence of coincidence therebetween, the address corresponding to that input point and its associated status are stored in a temporary store. A second or main memory is accessed by an address signal which comprises the address of that input point and its associated status which are read out from the temporary store, so as to supply information representative of that input point, for example, the name of a particular instrument and its associated status, to a recorder for the purpose of recording.