368 BELL SYSTEM TECHNICAL JOURNAL 



These are used with a standard tape sender to convert the tape record 

 to suitable electrical impulses. The use of tape gives flexibility to the 

 testing method since it is equally adaptable to syllable lists of any 

 desired type and length. It can also be easily arranged for synchro- 

 nous operation with a phonograph calling system. 



The operation of the automatic data handling apparatus may be 

 followed on the schematic diagram of Fig. 8. After a tape has been 

 threaded in the tape sender the caller starts the machine by pressing 

 a button. This causes a magnetic clutch to engage, which couples a 

 synchronous motor to the timing commutator, starts the speech and 

 noise volume measuring apparatus, resets the automatic volume indi- 

 cator and the other counting circuits, puts the room noise and line 

 noise phonographs into operation and signals the observers that a list 

 is about to be called. 



The timing commutator then causes the tape sender to advance 

 three steps and set up the first group of three duplex sets of decoding 

 relays, one set for the initial consonants, one set for the vowels and 

 one set for the final consonants. This group of decoding relays con- 

 nects the proper lamps to illuminate the syllable to be called on the 

 screen in front of the caller, the bank of lamps used for this purpose 

 being covered by a mask on which the various letters are printed. 

 The length of the flash is controlled in order to guide the caller in his 

 rate of calling. The translucent screen, with a syllable set up, may 

 be seen in Fig. 1. 



The caller now calls the first of the carrier sentences with the test 

 syllable inserted in the middle, starting to call as the syllable is flashed 

 on the screen and finishing when it goes off. The automatic volume 

 indicator simultaneously measures the volume of the sentences called 

 and soon after signal lamps indicate to the caller by how much he has 

 deviated from the prescribed volume. At the same time the auto- 

 matic speech volume recorder measures the speech volume on the 

 circuit under test. In the meantime the second group of decoding 

 relays has been set up and the observers are signaled by a light in 

 front of each that it is time to record what they think they have 

 heard. 



The equipment immediately in front of the observers is a set of 

 keyboards, one for each observer, which may be seen in Fig. 2. Each 

 keyboard is provided with a key for each of the speech sounds used. 

 On hearing the test syllable and receiving the signal the observers 

 operate in succession three keys corresponding to the three sounds of 

 the syllable as they understand them. The keyboards are so arranged 

 by interconnection with the decoding relays that if the proper keys are 



