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The traditional figure of merit in comparing the economics of telecommunication transmission systems has been the annual cost per voice-circuit mile at full capacity. While this is a useful measure in some types of comparisons, it does not provide a particularly meaningful measure of the costs borne by the users of a transmission system. The users are expected to pay the average costs. The average cost per voice-circuit mile provided by a transmission system is very sensitive to starting circuit requirements and the rate of growth in these requirements. The large cross section system can only be economical on routes with high starting circuit requirements and/or high growth rates. Lower capacity systems may be considerably more economical on routes with modest requirements. This paper investigates the annual costs of three modern transmission systems; TD-3, L-4 (20 tube), and L-5 (22 tube). Annual costs for each year and average annual costs for the program period are calculated and plots of the sensitivity of these costs to variations in the input assumptions are provided.