38 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



filters should have good phase response if they are to be used for a television 

 signal. 



The physical equipment used in this experiment is housed in three seven- 

 foot cabinet relay racks. One bay contains the sampler, the push-pull am- 

 plifier for driving the deflection plates of the coding tube, the coding tube, 

 the digit amplifier and slicers, and finally the translator. Another bay con- 



DIGITS 

 12 3 4 5 



DIGITS 



D 



□■=■ 

 □ 



-23 





DS 



-15- 



^D 



□ 



□ 

 n 



CONVENTIONAL 



REFLECTED 



Fig. 4— PCM code plates. 



tains the decoder, output sampler, attenuators, patching panel, output filter 

 and other test gear. The last bay contains the regulated power supplies. 



Coders and Quantizers 



We return now to further consideration of the coder and quantizer. The 

 coding tube used in these experiments was developed by Mr. R. W. Sears. 

 It is similar in many respects to one previously described by him in The 

 Bell System Technical Journal for January 1948. The older tube produced 

 the code on a time-division basis, while the new tube produces the code 

 simultaneously on a plurality of output digit collectors. 



The time-division coding tube which was used by Meacham and Peterson 

 in the 96-channel multiplex system first quantized and then coded the signal. 

 The simultaneous coding tube uses a different code which does not require 



