Digital telephone conference circuit - transforms continuously variable slope delta modulation input signals into slop numbers which are processed in PROM adder and subtractor

摘要

The seix-telephone channel conference system has an all-digital CVSD (continuously variable slope delta modulation) conference bridge-like circuit. The delta modulation pulses train in each channel is transformed into a series of slope numbers. The slope numbers are processed by the conference circuit addition function to provide zero insertion loss, then by the subtraction function to provide 100% cancellation of a talerps voice to his ear. Transformation involves a sequential three-bit algorithm. The adder includes a PROM.