384 



THK BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 



over-all carrier derived circuit. In keeping with the system objectives, 

 the over-all transmission of a carrier channel and its voice frequency 

 extension, using the 500-type telephone set, will be as good or better 

 than that obtained on long rural lines using phj^sical plant laid out by 

 the Resistance Design Method mentioned earlier. 



As shown in Fig. 27, the normal and staggered grouped frequency 

 arrangements used for repeater operation allow 30-db bare line attenua- 

 tion at the top freciuency (96 kc) between the central office terminal and 

 the first repeater or between repeaters, and about 30 db between the 

 last repeater and each remote channel terminal at the top frequency used 

 for that channel. Directional filter characteristics limit the repeater sys- 

 tem can use a maximum of four repeaters for a total line loss of about 150 

 db at 96 kc. However, noise and crosstalk requirements will permit no 

 more than two of the four repeaters to be used in the open-wire line, with 

 the last cable repeater at least one mile back in the cable from the cable- 

 open-wire junction, as show^n in Fig. 27. Spacings must be limited to 

 somewhat less than 30 db on certain line facilities such as B rural wire 

 to insure proper terminal regulation.^ 



CENTRAL 



OFFICE 



CARRIER 



TERMINAL 



CABLE AND 

 OPEN WIRE 



30DB AT MAX. FREQ. 



OF THE INDIVIDUAL 



CHANNEL 



CABLE OR 

 OPEN WIRE 



REMOTE 

 CARRIER 

 TERMINAL 



390 OHMS 



VF EXTENSION TO 



MOST REMOTE 



CUSTOMER 



(a) STACKABLE FREQUENCY ARRANGEMENT: NON-REPEATED 



CENTRAL 



OFFICE 

 CARRIER 

 TERMINAL 



CABLE 



1 MILE- 



A 



I 



30 DB 

 AT 96 KC 



: OPEN WIRE 



REMOTE 

 CARRIER 

 TERMINAL 



A 



i 



I 

 30 DB 



AT 96 KC 



(NOTE 1) 



NOTE t 

 CHECK MAXIMUM LOSS AT 30KC AND IF 

 LESS THAN GAIN IN REMOTE TERMINAL 

 TO CENTRAL OFFICE DIRECTION, PLACE 

 INPUT PAD EQUAL TO DIFFERENCE AT 

 INPUT OF REPEATER. 



/ 30 DB 390 



AT MAX. FREQ. OHMS 



OF THE INDIVIDUAL 

 CHANNEL (NOTE 2) 



NOTE 2 

 CHECK MINIMUM LOSS AT MINIMUM FRE- 

 QUENCY OF EACH CHANNEL FOR THE LAST 

 REPEATER TO REMOTE TERMINAL SECTION 

 AND IF THIS IS LESS THAN THE REPEATER 

 GAIN AT THAT FREQUENCY, PLACE PAD IN 

 OUTPUT OF TERMINAL TO BUILD SECTION 

 OUT TO REPEATER GAIN VALUE. 



(b) GROUPED FREQUENCY ARRANGEMENTS: REPEATED 

 Fig. 27 — PI carrier application ground rules. 



^ C. C. Lawson, Rural Distribution Wire, Bell Lab. Record, pp. 167-170, May, 

 1954. 



