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BELL SYSTEM TECHNICAL JOURNAL 



shielded wires is run to one location. Because of this congestion the 

 jacks in this bay are mounted or removed from the front. 



The concentration of equipment in the modem unit is made possible 

 by the small size of the copper-oxide bridges and the filters. Fig. 11,^, 

 shows twelve modem units for two systems on adjacent bays with space 

 left at the bottom for the six modems of a third system. 



Fig. 11 — Carrier equipment bays: "A" — channel; "B" — group; "C"- 



pilot supply. 



:arrier and 



The group modems are about the same size as the chanijel modems 

 and include a modulator, a demodulator, a transmitting amplifier, and 

 auxiliary receiving amplifier with associated filters. Fig. \\, B, shows 

 three units for three systems with space for six additional units at the 

 bottom of the bay. 



The carrier supply equipment for ten systems is mounted in one bay 

 as shown in Fig. 1 1 , C, which includes the regular and emergency gen- 

 erators, transfer unit, distributing equipment and pilot channel supply 



