Patent ID: 6317494
Filing Date: 2001-11-13
Classification: H04M,H04Q

Abstract:
A codec having a digital signal processor for performing coding and decoding functions, CHARACTERIZED BY an arrangement for ascertaining the impedance of a telephone line connected to said codec; comprising:means for applying a digital tone signal of known frequency and peak amplitude to said line;means for sampling the echo signal resulting on said line a predetermined number of times during the on-hook and off-hook states of said line;means for estimating from said samples the phase angle of said echo signal relative to said applied tone, said estimating commencing from an apriori starting value of phase angle;means for performing a least squares fit upon said samples;means for estimating from said samples the peak amplitude of said echo signal; andmeans for dividing the peak amplitude of said applied tone signal by said estimated peak amplitude of said echo signal to obtain the magnitude of the total impedance presented to said tone signal at said estimated phase angle.