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apparatus for a two-way circuit was mounted together on one rack. 

 The testing equipment and signaling apparatus were duplicated in 

 each repeater set. This apparatus, as well as the balancing networks 

 and other miscellaneous apparatus were mounted on the same rack 

 as the repeater. A unit of this type required about 10 square feet 

 of floor space. 



Fig. 3 shows the type of "through line" set which was standardized 

 in 1917 for use on open-wire lines. Fig. 4 shows a group of cord circuit 



Fig. 4 — Group of Six CordCircuit Repeaters and Associated Testing Unit 



sets of the same type of design, together with the testing unit. This 

 form of set was a great improvement over the earlier types. It em- 

 ployed, however, many of the same large types of individual pieces of 

 apparatus as were used in the former sets and the testing equipment, 

 which was mounted on the middle rack of the group, was required to 

 be duplicated for each group of 6 repeaters. This type of set has 

 been used in many of the smaller installations, but it has not met 

 the requirements for large cable installations. The average floor space 

 area required was about 6 square feet per set. 



Fig. 5 shows the proposed assembly of the type of telephone re- 

 peater which is now being developed for all classes of installations 



