RECORDING TRANSMISSION MEASURING SYSTEM 



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circuits. Figure 9 is a record of noise and Fig. 10 is a record of variations 

 in speech volume on a working circuit. The speech volume record is 

 of particular interest in showing graphically the variation of load on 

 the circuit during the different periods of the day and also the extreme 

 variations in the volume of different talkers. The recording system 

 was bridged on one end of the circuit so that a difference of several 

 db in volume level between the talkers at the two ends of the circuits 

 is to be expected. Figure 1 1 is a short-period record of speech volume 

 made at the high rate of paper feed. 



It will be noted that the width of the mark made by the heated 

 pointer is much greater in the case of the slow speed records than in 

 the case of the high speed records. In the slow speed records illus- 



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60 SECONDS 



Fig. 11 — Volume indicator record at high rate of paper movement. 



trated the points of interest are the peaks which the pointer reaches 

 frequently and the heat is adjusted so that a good record is made of 

 these peaks. The movement of the pointer is so rapid that no trace 

 is made between the peaks and the zero line. This feature is an ad- 

 vantage rather than a disadvantage since even with such a high speed 

 recorder the movement of the pointer is slightly behind the electrical 

 impulse which energizes it and for such tests as measurements of 

 speech volume the record between the zero line and the peaks or be- 

 tween any two peaks would not be extremely accurate. The exact 

 center of the broad line is directly under the heated wire. This point 

 is clearly distinguishable in the broad trace made by slow speed records. 

 It is expected that recording transmission measuring systems will 

 be of considerable value in locating intermittent troubles of very short 

 duration which are not easy to locate with manual arrangements. 



