1070 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



A gaiLssian shaped pulse at the output of the Hue is one of the most eco- 

 noniical to use and can have a maximum span of on(! timing interval at 

 its base. Howe^'er, in this case the envelope of a long consecutive se- 

 (juence of such pulses will show substantially no ripple. It can be readily 

 seen that in such a seciuence the onl}- timing control exercised by the 

 input upon the timing wnve comes from the first pulse. In the interest 

 of better timing and consecjuently better repeater performance one should 

 be content with narrower pulses at the repeater input. The resulting rip- 

 ple of the envelope of a consecutive pulse sequence allo^^"S each incoming 

 pulse some control over the repeater timing. 



3.0 REPEATER PERFORMANCE 



To check the performance of the regenerative repeaters a binary 

 code generator was built having a nominal pulse repetition rate of 672 kc 

 producing an eight digit code. Any code combination from the possible 

 256 can be selected or the code automatically changed at periodic inter- 

 vals reproducing all possible codes in orderly sequence. Random codes 

 may also be generated by making the absence or presence of a pulse 



52 



<rt 48 



44 



z 

 g 



z 



UJ 



40? 



< 36 



32 



0.56 MILES OF 

 EQUALIZED 32 GAUGE-, 

 CABLE USED IN TEST \ 

 ^— ^-n— n __Q_ I n I ' ■ 



10 



..-cr 



--?' 



2.3 MILES OF 



EQUALIZED 



19 GAUGE CABLE. 





20 40 60 80 100 200 400 



FREQUENCY IN KILOCYCLES PER SECOND 



600 



1000 



PULSE 



CODE 



GENERATOR 



-EQUALIZERS ^^ 



(b) 



Fig. 5(a) — Equalized characteristics of 19 and 32 gauge line. 

 Fig. 5(b) — Block diagram of equalizer for 32 gauge line. 



