APPLICATION OF ARTICULATION TESTING 



361 



As shown at the right in Fig. 4, the page printer of the data analyzing 

 equipment is located near the control board, so that the recording may 

 be followed as the list is called. As a further check on the operation 

 of the circuit a loudspeaker is mounted nearby. This is bridged across 

 the amplifier of the observer's circuit and permits an aural check on 

 the received speech and noise. The dial controlling the changing and 

 agitation of the transmitters is also located on the control board. 

 The push buttons shown are used for summoning the callers and ob- 

 servers. 



Caller's Control Circuit 



The caller's control circuit is shown schematically in Fig. 5 and in 

 greater detail in Fig. 6. A small condenser transmitter ^ is used for 



RECTIFIER 



INTEGRATING 

 CIRCUIT 



VOLTAGE DIFFERENTIAL 



DC MEASURING LEVEL 



AMPLIFIER CIRCUIT TOTALIZER 



CALLING BOOTH 



VOLUME 



INDICATOR 



SIGNAL LIGHTS 



CONDENSER 



TRANSMITTER 



AND PRELIMINARY 



AMPLIFIER 



NTERMEDIATE 

 AMPLIFIER 



TO TIMING 

 COMMUTATOR 



ARTIFICIAL 

 MOUTHS 



GAIN 

 CONTROL 



ARTIFICIAL 



MOUTH 

 EQUALIZER 



POWER 

 AMPLIFIER 



P^ 



~i7- 



'^r 



AUTOMAT- 

 ICALLY 

 OPERATED 



L 



TO AUTOMATIC 

 SPEECH AND NOISE 

 MEASURING APPARATUS 



u 



J 



Fig. 6^Schematic diagram of caller's control circuit. 



W 



picking up the speech of the caller. This, with its directly associated 

 preliminary amplifier, is located in the calling booth. The electrical 

 output passes through an intermediate amplifier, a gain control, a 

 power amplifier and an equalizer into one of a pair of artificial mouths. 

 One of the artificial mouths is shown mounted in front of a trans- 

 mitter under test in Fig. 7. The characteristics of the artificial mouth 

 and associated equipment are fully described in the paper referred to 

 previously. 



3 "An Efficient Miniature Condenser Microphone System," H. C. Harrison and 

 P. B. Flanders, B. S. T. J., XI, p. 451, July, 1932. 



