534 



BELL SYSTEM TECHNICAL JOURNAL 



The right-hand portion of the same figure shows the synthesis of 

 this signal from component parts. From this figure it may be seen 

 that by the time the seventh harmonic (curve q) or even the fifth har- 

 monic (curve p) has been added, there is a resemblance between the 

 resultant and the original wave. 



START 12 3 4 5 STOP 

 TELETYPEWRITER D SIGNAL 

 AT 368 OPERATIONS PER MINUTE 



I EIGHTH 49,1 



j NINTH 55.2 



/\/\j\r\/\/\j\/\/y^K 



k TENTH 61.4 



m H-C 0-12.3 



1 [>C COMPONENT + FIRST HAR- 

 MONIC (a + b) 0-6.1 



q p+g + h 0-4311 



r q + i+j + k 0-61.4 



Fig. 2— Analysis of components of a teletypewriter "D" signal. Numbers on har- 

 monic curves are frequencies in cycles per second. 



As mentioned previously, the total intelligence transmitted by a 

 given telegraph signal may be contained in a frequency band lying 

 between zero and the fundamental frequenc\' of the shortest signal 

 element, i.e., the frequency at which the duration of the shortest 

 element is a half cycle. In 60-speed teletypewriter transmission the 

 shortest signal element is of approximately 0.022 second duration, 

 and its fundamental frequency is about 1/0.044 = 22.7 cycles per 



