596 BELL SYSTEM TECHNICAL JOURNAL 



shows the principal equipment groups involved in a typical long 

 carrier system. The particular system illustrated is one of those 

 between Minneapolis and Chicago, with repeater stations at Waterloo 

 and Dubuque, Iowa. The carrier repeater equipment is ordinarily 

 additional to voice-frequency repeater apparatus used in the wire 

 line as mentioned above and is connected so that the high-frequency 

 currents for the carrier pass around the voice-frequency repeater. 

 The wires concerned are employed also for d.-c. telegraphy by the 

 use of composite sets. 



The principal groups of equipment involved in such a system 

 include the carrier sending and receiving equipment and filters at 

 the terminals, the repeater amplifiers and filters at the intermediate 

 stations, and the line equipment and pilot channel equipment at all 

 points. In addition, power supply equipment and testing equipment 

 are required at all points, and voice-frequency and signaling apparatus 

 at the terminals. 



The total amount of equipment involved in a typical carrier tele- 

 phone system shown in Figure 15, exclusive of the power supply, 

 includes altogether about 188 panels assembled on racks equiv^alent 

 to 14 bays ^ and occupying a total floor space, including aisle space, 

 of about 84 square feet. If the three channels which the system 

 ordinarily provides were obtained by regular wire circuits, the ofifice 

 equipment might amount altogether to about 36 panels and 1.7 bays, 

 occupying about 10 square feet. Thus, in a typical case, about eight 

 times as much ofilice equipment, other than that for the power supply, 

 might be required to furnish a given number of facilities by carrier 

 telephony, in comparison with that needed for the equivalent number 

 of ordinary wire circuits. 



Terminal Station Installations. The principal equipment groups 

 comprising a terminal of a type " C " system are indicated in Figure 19. 

 A typical assembly showing a majority of these equipment groups is 

 given in Figure 20. This does not include the signaling equipment, 

 the pilot channel, or the power equipment. A rear view of this same 

 assembly is shown in Figure 21. 



Returning to Figure 20, the right-hand bay contains the apparatus 

 comprising two channel terminals. The middle bay includes the 

 third channel apparatus and the terminal transmitting and receiving 

 amplifiers and directional filters which are mounted in the upper 

 portion. The box-like units on both bays are the band filters and 

 directional filters. On the right-hand bay the upper of the panels 



'A bay consists of two channel or I beam uprights, ordinarily about Hi feet 

 high, and spaced so as to mount unit panels 19 inciies wide and of varying height. 



