SG Undersea Cable System: Terminal Transmission Equipment

The terminal transmission equipment (TTE) for the SG Undersea Cable System provides the vital interface between the inland telephone network and the undersea link. Interconnection to the domestic network is at the basic supergroup level; thus, the TTE consists of frequency-di2471 vision multiplex and wideband line equipment (including a directional filter that provides a physical 4-wire to equivalent 4-wire conversion) (Fig. 1). The transmitting multiplex serves to frequency-translate fifty-plus basic supergroups, combining them to form what we call the "baseband." The receiving multiplex performs the inverse operation. The wideband line equipment provides its customary functions of signal preemphasis and deemphasis, equalization, level adjustment, and the like. Following the conventional equivalent 4-wire undersea cable terminology, the terminal stations at opposite ends of the system are designated A and B. Low-band transmission in the A-to-B direction is at baseband frequencies directly. In the opposite direction, the high band is formed by one further stage of frequency translation of the baseband, which takes place in the wideband line equipment. The principal system parameters influencing TTE design are summarized below: (t) Nominal frequency band (corresponding to 4000 3-kHz voice channels): Low band 800 to 13,300 kHz, High band 16,700 to 29,300 kHz. (ii) Possible extension to: Low band 500 to 13,900 kHz, High band 16,100 to 29,500* kHz. (iii) Operation with either 3- or 4-kHz voice channels, or a combination of the two.