in a data compression system , a digital signal comprising a series of digital samples and a sampling datum associated with each digital sample is received by a decoder . the sampling datum indicates the sampling interval of the associated digital sample . the decoder includes a microcomputer for storing the digital signal into a memory and reading each digital sample and the associated sampling datum . the digital sample is divided by the sampling datum to derive a quotient which indicates the slope of the signal to be recovered . the quotient is integrated by an integrator to provide interpolation between successive sampling points , so that the original signal is approximated by a plurality of line segments .