620 



BELL SYSTEM TECHNICAL JOURNAL 



entire preceding consonant is clipped of¥. The clipping is sometimes 

 disconcerting and may impair the intelligibility of the transmitted 

 speech. If the relay is made sensitive enough to operate on the f's 

 and s's another difficulty arises. Relatively low values of room noise, 

 noise induced on wire lines, or the speaker breathing into the micro- 

 phone may produce enough energy to actuate the relay during listening 

 periods, thus interrupting the conversation. In other words, if the 

 relay is sensitive only to the loud sounds clipping will occur, while if 

 sensitive to the weaker sounds it may be actuated by noise. These 

 difficulties are surmounted by using the more complex circuit termed 

 the "Vodas" as indicated in Fig. 6. 



RECEIVING 

 AMPLIFIER 





RECEIVING 

 DELAY 



HYBRID 

 COIL 



SUB- 

 SCRIBER 



TOLL 

 ^ SWITCH- 



_rr:^L. board 



NET- 

 WORK 



\v 



RADIO 

 RECEIVER 



RECEIVING 

 DETECTOR 



TELEPHONE 

 OPERATOR 





RECEIVING 



ENERGIZED 



SWITCH V 



TRANS- 

 MITTING 

 AMPLIFIER 



^ 



r 



y, 



, .TRANSMITTING 



ENERGIZED 

 ~j^ SWITCH 



TRANS- 

 MITTING 

 DETECTOR 



L-) 



RADIO 

 STATION 



TRANS- 

 MITTING 

 DELAY 



SHORT- 

 CIRCUITING 

 U SWITCH 

 O 



^ 



RADIO 

 TRANS- 

 MITTER 



Fig. 6 — Vodas (voice operated device anti-singing). 



In this diagram the transmitter is located on the bottom branch in 

 which there is interposed a transmitting delay circuit. The incoming 

 speech after passing through the transmitting amplifier operates relays 

 by means of the transmitting detector. The relay is so adjusted as to 

 be operated by the louder sounds in the voice but not by noise. While 

 it is operating upon the vowel sound following a consonant, the con- 

 sonant may be on its way through the delay circuit so that the relay 

 which normally shuts ofif signals to the transmitter will actually clear 

 the path to the transmitter in time for the first sounds of a word in 

 most cases. The utilization of the delay circuit can therefore practi- 



