Digital filter for pulse code modulation signals

Claim 1

A digital filter for filtering a plurality of pulse code modulation signals appearing on separate input lines comprising: sampling means for sampling each said input line in succession; analog to digital means for sequentially converting the samples from said sampling means into digital form; a plurality of serially connected single stage registers wherein the number of registers is equal to the number of said input lines, having the input to said plurality of serially connected registers connected to the output of said analog to digital means; an adder means having one input connected to the output of said plurality of serially connected registers and a second input connected to the output of said analog to digital means for adding successive samples from a common one of said input lines and for adding samples from a different one of said input lines in succession; a dividing means responsive to the output from said adder for averaging the output from said adder by dividing said adder output by two; and digital to analog means for converting the averaged signal from said divider into analog form.