ORGANIZATION OF HIGH-SPEED DATA-TRANSMISSION IN PRIMARY NETWORK CIRCUITS

The existence of network circuits in an analog network has made it possible to lease to a customer (such as modern data processing networks) a primary network circuit (PNC) with a nominal bandwidth of 60-108 kHz. Using a PNC as the transmission medium in place of a primary broadband circuit (PBC) permits the establishment of high-speed data transmission in a short time period without reconstruction or technical outfitting of existing communications systems. A PBC used for high-speed data transmission at 48-144 kbits/s [1-2] has been developed based on a compound PNC (operating frequency range: 60.6-107.7 kHz) by means of baseband equipment at its input and output, and by replacing the tandem equipment employing amplitude correction by tandem equipment employing amplitude-phase correction. However, the existing primary network is not equipped with tandem equipment employing amplitude-phase correction, and its introduction requires additional expenditures. Recommendation H.14 of the CCITT [3] has proposed that, in addition to a PBC, a PNC based on a secondary or quaternary group circuit be used for high-speed transmission. In this case correction of the significant distortions to the frequency responses of the PNC is required in the terminal equipment. A signal converter (SC) that satisfies CCITT Recommendation V.37 is used as the terminal equipment for transmitting data in the PNC at a specific speed in the order of 3 bit/s.Hz.