414 



K. A. OLSON, F. S. BRACKETT, K. G. CRICKAUD 



slope has actually been improved and the "personal equation" 

 eliminated as well. 



A block diagram of the system is shown in Fig. 2. The discrete 

 or stepwise character of the method presents novel problems in re- 

 cording. A composite timing unit with five cams provides the answer. 



Fig. 3. Calibration records: Part one, slope produced by known potential change 

 from stepping switch. Part two, corresponding rate record. 



Thus it (1) generates the square potential pattern, (2) initiates time 

 control of stepping switches and also of light, (5) cuts off the ampli- 

 fier during the period of possible overload, (4) connects the grid con- 

 denser of the first output stage during the terminal portion of the 

 negative phase, (5) grounds the grid condenser of the second output 

 tube for a part of each cycle so that it responds only to the change, and 



