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BELL SYSTEM TECHNICAL JOURNAL 



Fig. 3- 



-Loading coil for buried wire before filling outer case, showing the splicing of 

 the rubber covered stubs to the lead-out wires from the inner case. 



tubes. This outer can is then filled with a moisture-proof compound 

 and given a dip coating of moisture-proof enamel. The operation of 

 splicing the loading coil into the line wire then inv^olves making two line 

 wire splices as above described. 



The one-thousand-cycle attenuation of this 17-gauge buried wire 

 after seven days water immersion and at 70° F. is about 1.1 db per mile 

 for the non-loaded line and the corresponding attenuation of the loaded 

 line is about .49 db per mile. The characteristic impedance of the 

 non-loaded line at one thousand cycles and under the same conditions 

 as above would be 275/40° and of the loaded line would be 525/8°. 

 The nominal cut-off frequency of the loaded circuit is 3600 cycles. 



Layout of Buried Circuits 

 At the present time, the most promising use of buried wire in the 

 telephone plant appears to be for rural distribution on routes requiring 

 one or two pairs. These routes would commonly have a number of 

 party line subscribers, each subscriber being bridged on the buried 

 circuit. For the most part, it has been found preferable to follow the 

 route of existing public roadways, laying the wire in the shoulder of the 

 road. Installing the wire on right-of-way across private property is 

 advantageous under some circumstances, however. At points where a 

 service connection is to be made, there is the alternative of bridging a 

 service lead across the through circuit or looping the circuit into the 

 subscriber's house, the latter being preferred where the house is a 

 short distance from the through route. Where a bridged connection 

 is to be made, it has been found desirable to bring the wires up above 



