TELEPHONE EQUIPMENT FOR LONG CABLE CIRCUITS 115 



mounted on separate racks while the plate batteries for the vacuum 

 tubes were mounted in an adjacent enclosed cabinet. The floor space 

 requiied for a two-way repeater employing this type of apparatus 

 was in the neighborhood of 15 square feet per unit, including the usual 

 allowances for aisle space and associated apparatus. 



Fig. 2 shows the first type of vacuum tube telephone repeater 

 designed [or commercial manufacture. The particular unit shown 

 is a single "through line" set, that is, one which remains connected 



3 — Standard Through Line Repeater for Open-Wire Use 



to a through circuit at all times instead of being used at a switching 

 point to establish built-up connections at the will of the operator, as 

 a "cord circuit" repeater is used. The "cord circuit" repeater of 

 the same type was similar in arrangement and dimensions to the 

 "through line" repeater shown. In this type of repeater, all of the 



