Structure of a Text-based TEDS data block TEDS Identification Header The number N of different language blocks in this TEDS Language block description This block is repeated N times Language code from ISO 639 (two letters in USASCII) Language offset Language length = LL Enumeration identifying the compression technique used. Non-displayable data checksum This is a class of optional TEDS. The function of these TEDS is to provide information for display to an operator. There are six TEDS listed in Table 17 that fall into this category. They are the Meta-Identification TEDS, TransducerChannel Identification TEDS, Calibration-Identification TEDS, Commands TEDS and the Location and Title TEDS and the Geographic Location TEDS.