A technique applied to a DS1 frame to ensure pulse density requirements are met, where bits 2 through 193 of each frame are scrambled to minimize the occurrence of all-zero octets. When an all-zero octet is contiguous to another octet with zeros and they would combine to violate the ones density requirement, an algorithm is invoked where some all-zero octets are replaced by an address chain. The reverse algorithms are performed by the receiving terminal.