the n-1 carrier system 5 



Compandor 

 While the compandor principle is not new, it is believed that, for the 

 first time, full advantage of the compandor has been taken in the design of 

 a carrier system. To assist in explaining these advantages, general com- 

 pandor principles will be reviewed in the light of the present development. 

 The 1 A compandor \ designed more than ten years ago, has had considerable 

 usage in open-wire carrier systems in reducing crosstalk, but in the N 



GROUP CARRIER 

 304 KC 



260 KC— 



12p-»-256 

 11'DU. 248^5 

 HIGH-GROUP 10[>y 240 2(0 

 BAND /9[>V232^y 



OF LINE / vrWpiR ^>: 

 TRANSMISSION/ l^f^'^^^'^ 



6[}*^208i 



5 [>♦ 200 ct; 



40-^192 y 



/ 3[>*184 ^? 

 / 2CK176 < 

 ' 1&^168 ^ 



164KC-I \ \ 



/ 



VOICE TO 



CARRIER 



MODULATION 



AND 



DEMODULATION 



IN CHANNEL 



UNITS 



/ 



/ VOICE 

 / CHANNELS 



ODDDDDDDDDDD 

 12 10 8 6 4 2 



\ \ 

 140\KCa- , 



\ 1tl—136>- 

 \ 2D-^128 5^ 

 \ 3[>*120SI2 

 \ 4D-»-I12 3-1 



5[>*104 



0(J 



\6D-*-96 DCO 



\7[>*88 "^g 



>l>*80 ^E 

 9D— 72 s 

 iqD-^64 oc- 



120-^48 



44 KC — 



LOW-GROUP BAND 



FREQUENCIES OF 



LINE TRANSMISSION 



CH 12|-k260KC 



260 KC/ 



EAST-WEST 

 OUT---"^ 



LOW-GROUP 

 CH)2 



CH 12 



WEST- EAST 



IN--^^^^ — 



HIGH-GROUP 



CH 1 



\ 

 44 KC 44 KC^ 



LOW-HIGH REPEATER 



,260 KC 



CH 1 

 EAST-WEST 



OUT-— "^ 



LOW-GROUP 



CH 12 



I-K44 KC 44 KC 



HIGH-LOW REPEATER 



LOW-GROUP 

 CH 12 



Fig. 1 — N-1 carrier frequency allocations for terminals and repeaters. 



system a more compact and cheaper unit was needed with requirements 

 revised to match the reduced maximum length of circuits. The word com- 

 pandor is a contraction of compressor and expandor — the compressor in the 

 transmitting terminal compressing the input range of speech volumes for 

 passage over a wire or radio transmission medium where a variety of noise 

 and crosstalk interferences are present — the expandor in the receiving 

 terminal expanding the received range of compressed speech volumes to the 

 original range. A 20-28 db noise advantage is derived, and can be explained 

 as follows: Weak speech volumes most susceptible to system disturbances 

 are lifted and carried at higher level over an intervening noisy medium. 



1 Application of Compandors to Message Circuits, C. W. Carter, Jr., A. C. Dickieson 

 and D. Mitchell— ^./.£.E. Trans., Vol. 65, pp. 1079-1086. 



