A method for more efficient use of the 4B voice/data lines with application to the proposed AAP teleprinter
William P. Dotson, Jack Harvey Wilson · NASA Technical Reports Server (NASA) · 1970
This document presents a technique for transmitting digital data within the unused spectrum on voice communications channels.The channels may be used simultaneously for both voice and digital data.Necessary equipment to frequency share the channel is shown, and test results that demonstrate the feasibility of the technique are shown.. --..