International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / This paper describes the design and characteristics of a digital voice encoding circuit that uses the continuously variable slope delta (CVSD) modulation/demodulation method. With digital voice encoding, the audio signal can be placed into the pulse code modulation (PCM) data stream. Some methods of digitizing voice can require a large amount of bandwidth. Using the CVSD method, an acceptable quality of audio signal is obtained with a minimum of bandwidth. Presently, there is a CVSD microchip commercially available; however, this paper will describe the design of a circuit based on individual components that apply the CVSD method. With the advances in data acquisition technology, increased bit rates, and introduction of a corresponding MIL-STD, CVSD modulated voice will become more utilized in the flight test programs and a good knowledge of CVSD will become increasingly important. This paper will present CVSD theory, supported by graphical investigations of a working circuit under different conditions. Finally, several subjects for further study into CVSD will be addressed.