On the accuracy of holding time measurements
Imre Molnar · Transactions of the American Institute of Electrical Engineers · 1951
Fundamentally, telephone traffic is the sum of accumulated holding times of switching channels. From this simple statement two important conclusions can immediately be drawn. First, that telephone traffic is completely equivalent to the length of occupancy of the switching channels; that it may be expressed in any convenient unit of time; and that the same traffic or occupancy can be made up by many calls of short holding times each, or a few calls of long holding times each, or in any conceivable mixture of these as long as the sum of the individual holding times add up to the total length of occupancy. Second, since a channel naturally cannot be occupied for more than one hour in any single hour, the traffic carried per channel in one hour cannot exceed one traffic unit. From this it is argued that any measurement of traffic can be reduced in the last analysis to the measurement of time, more specifically to the measurement of accumulated holding times. From the preceding it will be understood that the switch count process is a particular method of time measurement by sampling, and its accuracy can be appraised by comparison with direct measurement of time, for instance, by a clock, where the latter term is used in its broadest possible interpretation. If the laws governing the accuracy of peg count methods and holding time measurements are determined, we have the necessary tools available by which the accuracy of traffic measurements can be appraised. The former was recently studied and published by the author, who found that the commonly used peg counting methods provide an exactness well within that required for traffic measurements.