LOW DISPARITY BIPOLAR PCM SYSTEM

摘要

There is disclosed herein a signalling process for a PCM transmission system having reduced disparity, that is, a substantially equal number of binary "1" digits for the pulse stream. This is accomplished by complementing normal PCM words if the number of binary "1"s in a word are less than n/2, where n is equal to the number of digits per word, and using alternate-polarity bipolar code PCM transmission. In accordance with the present invention the complementing of PCM words is indicated by a polarity violation of the bipolar code of the first digit of the complemented words. This results in two pulses of the same polarity being adjacent each other rather than alternate polarity as is usual in alternate-polarity bipolar PCM. Transmission and reception circuits are also disclosed to implement the PCM signalling process of this invention.