An evaluation of digital transmission techniques for miltiple access to a communication satellite. Specific features of digital techniques are examined: time-division multiplexing, error correction codes, analog-to-digital conversion methods, and synchronization problems. Difficulties encountered in time-division multiplexing include deriving timing and controlling intersymbol interference. Error correction codes evaluated form a system viewpoint are found to be relatively poor when measured in decibel units. Delta modulation as an analog-to-digital conversion technique does not require the frame synchronization of pulse code modulation. It is less expensive and well suited to speech encoding.