Regulation of frequency for measurement purposes

IT happens very often that it is desirable or necessary to transmit a quantitative indication to a more or less remote point. For instance, in a modern power system with its various sources of power, the load despatcher may wish to know the amount of power generated in a station perhaps several miles away, so that he may be able to better distribute his load. In addition, it may be desirable to regulate automatically the distribution of power as well as limit the amount that is received from a distant point. In this connection the problem may not be simply that of limiting the indicated power but of measuring and limiting the integrated demand over a definite time period. Of a different nature is the problem of recording at widely distributed points various operations in an industrial plant so that the results can be compared on the basis of the exact time of occurrence.