Field 29 INSTRUMENT CODE. Assigned by NODC. Appears only on BT'S processed without TSC correction. This code will allow computer determination of TCS and correction of temperatures by computer. 30 INSTRUMENT TYPE. Mechanical BT is coded as O1. 31 CARD COUNT. Number of cards punched. Number shown should match the number of the last detail card (Field 45.) 32 UNIT CODE. See Table IX. The unit code entry denotes the units of depth, temperature sounding, etc., as punched on the INPUT card. Note that the depth of specific temperature entries on the detail cards must be determined by use of the correct overlay template; the unit code is the key for selecting the correct template. 33 ORIGINATOR'S CRUISE NUMBER. 34 ORIGINATOR'S SLIDE NUMBER. 35 SHIP'S NAME. 36 SHIP'S NUMBER. This is an optional entry. At this time, entry is determined by the originator or cognizant institute. 37-40 These fields are intended for future use. They will allow cross-reference with pertinent oceanographic station data. 41 FOR NODC USE ONLY. (The entry NODC denotes that NODC has assigned a number in lieu of the originator's cruise number. Used only where digitization is performed geographically rather than by cruise.) 42 CARD TYPE 02. Reference card identifier. 43 BT TEMPERATURE VALUES. BT temperature values to tenths of a degree (°F or °C) at successive depths negative temperatures are preceded by a negative sign. To determine units of depth, temperature and depth of specific temperature entries, see Field 32, Table IX, and use correct overlay template. 4.