TRANSISTOR BINARY PULSE REGENERATOR 1071 



ill anj^ time slot dependent on the polarity of random noise. The output 

 (if the code generator was made substantially the same as the outputs 

 I »f the repeaters both in shape and amplitude. Two types of transmission 

 line were used, a line from a 51 pair 19 gauge exchange cable and a pair 

 from a 32 gauge experimental cable. The nominal lengths of cable be- 

 tween repeaters was 2.3 miles for the 19 gauge and 0.56 miles for the 32 

 nauge cable. Fig. 5(a) shows the equalized characteristics for both these 

 lines. The important differences between the two is a greater flat loss 

 w ith a better high frequency characteristic for the 32 gauge cable. This 

 was advantageous in the study of error production and consequently, 

 the error measurements were all made with this cable. The 19 gauge 

 characteristic represents about the maximum high frequency loss that 

 can be tolerated by these regenerative repeaters. 



The performance of the regenerative repeater circuit can best be shown 

 by photographs taken from a cathode ray oscilloscope representation. 

 Plate I shows the effect of the 19 gauge line equalizer. The output pulse 

 (1) transmitted over the unequalized line has become very broad, ex- 

 tending over several timing intervals, which are indicated by small 

 pips along the trace. The addition of the equalizer reduces the width 

 of the received pulse (2) until it is somewhat narrower than the normal 

 pulse interval of the code. Plate II shows a series of photographs taken 

 of the input and output of a repeater with or without interference added 

 at the repeater input.* A signal code at the input of the repeater is 

 shown on (a) and its regenerated output on (b). A sinusoidal inter- 

 ference having a frequency of about 100-kc pictured on (c) is added to the 

 signal as represented on (d). The regenerated output of input (d) is 

 shown on (e) . From these it can be seen that while interference does not 

 change the pulse shape or size, it does produce a phase modulation. 



Plate I — Single pulse at output of 2.3 miles of 19 gauge cable. 1 — Unequa- 

 lized. 2 — equalized. 



* The input signal of this and some of the following photographs was taken 

 with the repeater in an inoperative condition. This was done in order to avoid the 

 resulting complexity that results when both the quantized feedback and timing 

 wave are added to the combinations of incoming signal and interference. 



