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BELL SYSTEM TECHNICAL JOURNAL 



made so that each curve can be torn off as soon as made, the paper 

 coming out of a slot in the front of the case shortly after it has passed 

 over the point of recording. The mechanism will accommodate a 

 400-foot roll of paper, which is sufficient for about 400 transmission 

 frequency runs or for one month's operation at the slow speed. A new 

 roil can be inserted in a very short time. 



As previously stated, the deflection of the meter in db is plotted 

 against frequency for some classes of measurements and against time 

 for others. Since the same meter is used for many types of test it is 



Fig. 5 — Ruling and marking features of recorder. 



preferable not to have the paper ruled for either frequency or time 

 but to apply frequency or time markings after the record has been 

 made. This is done by making reference marks on the margin of the 

 paper as it goes through the recorder, and using them as indices to 

 correlate the frequency or time and the record. As the paper passes 

 over the bar, the marks are made by means of the electro-magnetic 

 device shown in Fig. 5 at the right of the paper roll. As previously 

 mentioned, when transmission-frequency characteristics are measured 

 a tuned circuit causes a mark to be made when a particular frequency 



