An accurate voice-frequency-level calibrating set for field use
William T. Cochran · Transactions of the American Institute of Electrical Engineers Part I Communication and Electronics · 1963
In order to maintain the accuracy of loss measurements commensurate with the requirements of direct distance dialing (DDD), very accurate test tones are needed. This paper describes a rugged, portable calibrating set used to insure the accuracy of the test tones. A telephone craftsman may use this set to adjust the level of a signal with 0.3% accuracy. A means for analytically determining the accuracy of such a set is given in the Appendix.