0.3 to 30 cps . In practice, the speed-up is much greater. Records are 

 made in the field at 1-7/8 ips . Through a process of playback (at 60 ips) 

 and re-record (at 1-7/8 ips), a speed-up of 32 times is achieved. When 

 this new signal is played through the analyzer at 30 ips, an additional 

 speed-up of 16 times is realized. The total speed-up is 512 times true 

 time and the apparent frequency scale of possible interest becomes 15.4 

 to 1540 cps. Lower recording speeds (less than 1-7/8 ips) are becoming 

 commercially available, and it may soon be possible to do away with the 

 re-record process in the SEADAC. 



While the tape is being re-recorded on the loop recorder, it is 

 simultaneously recorded (at 5 mm/sec) on an 8-channel Sanborn strip 

 chart recorder (see Figure 1) . This paper display (Figure 2) is not 

 suitable for analysis but certainly illustrates what is on the tape. 

 The information on the paper is completely described by writing in 

 the experimental constant information, including calibrations, for each 

 channel. In this form, the visual data may be used in deciding the 

 proper analysis constants and will also serve as a check on analysis 

 results, at least for orders of magnitude. 



Each run constitutes a page in the "book" which is the recorded 

 history of the experiment. A summary sheet describing the trial is 

 attached to each book at the termination of the project, before it 

 is filed. 



The magnetic tape is likewise separated into runs and each run is 

 spliced into a loop. A typical run which is 20 minutes in duration 



7 



