A modulation technique for encoding an analog-to-digital signal conversion. Delta modulation samples the analog signal at precise points in time, converting the signal into a series of segments, each of which is compared to the original signal to determine if the amplitude changes. If there is a change in relative amplitude from one sample to the next, a series of bits is sent to indicate the extent of the increase or decrease in signal amplitude. If there is no change in amplitude, no bits are transmitted. Variations on the theme of delta modulation include continuously variable-slope delta (CVSD) modulation. See also amplitude, CVSD, delta, encode, and modulation.